Biology subjects

Moore, B. S.

Publications and source records attributed to Moore, B. S..

18 recordsLinked to original sources

bioRxiv2026

Convergent routes to haloterpenoid biosynthesis in red algae: identification of non-canonical UbiA-type terpene synthase gene clusters in the genus Laurencia

Red algae produce structurally diverse haloterpenoids unique to seaweeds, yet the enzymes responsible for generating many of their core terpene scaffolds remain unknown. Here, we report the identification of red algal UbiA-type terpene synthases (UTSs), a noncanonical enzyme family recently associated with terpene biosynthesis in bacteria and fungi. By prioritizing UbiA candidates located near putative biosynthetic genes, we identified eight candidate gene clusters across two red algal species, Laurencia pacifica and Laurencia subopposita. Using the heterologous host plant Nicotiana benthamiana, we show that the UbiA genes act as non-canonical TSs and that two UTSs produce the sesquiterpene bisabolene. The discovery of the bisabolene UTSs, LsUTS-2 and LpUTS-2, lays the foundation for laurane and chamigrane-type sesquiterpenoid production, addressing a prior biosynthetic quandary that bisabolene is not produced by established red algal class I TSs. Phylogenetic analyses distinguish the red algal UTSs from canonical UbiA prenyltransferases involved in primary metabolism and suggest they were acquired outside the red algal lineage. These findings expand the known distribution of UTSs and establish a previously unrecognized route to red algal terpene scaffolds.

biochemistry↗

bioRxiv2026

Genomic detection of domoic acid biosynthesis uncovers expanded toxigenic diversity across Pseudo-nitzschia diatoms

Domoic acid (DA) production by diatom genus Pseudo-nitzschia causes recurrent harmful algal blooms with major consequences for marine ecosystems, fisheries, and human health. Predicting DA risk remains challenging because toxin production varies across morphologically similar and cryptic lineages. Consequently, morphology or single marker genes often fail to resolve toxigenic potential. Here, we expand genomic resources for Pseudo-nitzschia by generating and compiling high-quality genomes spanning diverse species and biogeographic origins, establishing a genus-wide phylogenomic framework to investigate the distribution and evolution of the DA biosynthesis (dab) gene cluster. Among chemically characterized strains, the dab pathway was detected in species only with confirmed DA production. While the cluster exhibits a conserved core structure, several lineages display signatures of ongoing evolution, including intronization, locus rearrangement, and pseudogenization. One striking example of dab variation occurs in toxigenic P. australis strains, in which its biochemically validated isodomoic acid A synthase-encoding gene dabC is located outside the dab locus. Metatranscriptomic surveys reveal widespread environmental dab expression across size classes and species, implicating taxa not typically associated with environmental DA events, such as P. cf. obtusa and P. cf. plurisecta. To connect dab expression with chemical output, nutrient limitation experiments in the historically inconsistent DA producer P. pseudodelicatissima combined transcriptional profiling and nontargeted metabolomics demonstrating coordinated dab expression across distinct co-expression modules and DA accumulation in response to silicon limitation. Together, these results refine the phylogenetic scope of DA production and provide a genome-resolved basis for improved molecular monitoring of toxigenic diversity.

genetics↗

bioRxiv2026

Computational pipeline reveals nature's untapped reservoir of halogenating enzymes

Microbial halogenated natural products (hNPs) hold ecological, agricultural, and biomedical relevance. The hNP-producing potential of the organism can be assessed by the precise prediction of biosynthetic enzymes, yet the detailed annotations of halogenases are often missing from genomic and metagenomic data. We created a manually curated database (https://halogenases.secondarymetabolites.org/) containing information on the halide-specificity, role, and position of verified catalytic residues and results of the mutagenesis studies of more than 120 experimentally validated or in silico inferred halogenases. The collection of experimental data supports a computational pipeline that allows the family-, substrate-, and halide-scope-level annotation of halogenating enzymes by relying on catalytic residues, conserved motifs, and profile Hidden Markov Models (pHMMs). Our analysis with sequence similarity networks (SSNs) highlighted several underexplored clusters in the UniRef50 database. Such finding was a halogenase from Rhodopirellula baltica (RhobaVHPO) previously labelled as a hypothetical chloroperoxidase, which clustered apart from the known chloroperoxidases and bromoperoxidases, but accepted chloride and preferred bromide. Our database and workflow provide extensive and scalable solutions for the systematic and precise annotation of halogenating enzymes in genomic and metagenomic data. The in-depth categorization of halogenases will improve the chemical structure prediction of microbial hNPs, supporting ecological assessments and natural product discovery. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/700248v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@ebae51org.highwire.dtl.DTLVardef@10188f0org.highwire.dtl.DTLVardef@1c55684org.highwire.dtl.DTLVardef@b311bd_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

bioRxiv2025

Structural and biochemical basis for cannabinoid cyclase activity in marine bacterial flavoenzymes

The marine bacterial flavoenzymes Clz9 and Tcz9 can process cannabigerolic acid (CBGA) to the minor cannabinoid, cannabichromenic acid (CBCA), however, the mechanistic details of this extrinsic transformation are still obscure. Here, we report a thorough analysis of CBCA-formation by Clz9 and Tcz9 through high-resolution crystallographic characterization, biochemical analysis, and spectroscopic interrogation. Our work reveals that Clz9 and Tcz9 use different biochemical mechanisms from Cannabis cyclases and each other in their production of CBCA. Collection of a high-resolution substrate-bound structure, the first for any cannabinoid cyclase, provides key insights into how active site architecture affects substrate binding and stereoselectivity. Engineering approaches improve the stereoselectivity of CBCA formation by Clz9 and Tcz9, providing access to (R) and (S)-CBCA. Collectively, our work advances understanding of enzymatic cannabinoid formation and cements Clz9 and Tcz9 as two unique members of the BBE-like enzyme family with encouraging potential for biocatalytic cannabinoid production applications.

biochemistry↗

bioRxiv2025

Domoic acid biosynthesis and genome expansion in Nitzschia navis-varingica

Production of the neurotoxin domoic acid (DA) by benthic diatom Nitzschia navis-varingica poses considerable health and economic concerns. In this study, we employed whole genome sequencing and transcriptomic analyses of regionally distinct N. navis-varingica strains to unravel the genomic underpinnings of DA biosynthesis. Our analyses revealed sizable genomes--characterized by an abundance of repetitive elements and noncoding DNA--that exceed the size of any other pennate diatoms. Central to our findings is the discovery of an expanded domoic acid biosynthesis (dab) gene cluster, spanning over 60 kb and marked by a unique organization that includes core genes interspersed with additional genetic elements. Phylogenetic and syntenic comparisons indicate that transposition events may have driven the expansion and reorganization of this cluster. Biochemical assays validated that the kainoid synthase encoded by dabC catalyzes the formation of isodomoic acid B, thereby establishing a distinct chemotype in contrast to the DA profiles of planktonic diatoms. These results highlight the evolutionary trajectory of DA biosynthesis in diatoms and potential advantages conferred by genome expansion and enzyme diversification in dynamic marine environments. IMPORTANCEDomoic acid (DA) is a potent neurotoxin produced by marine micro- and macroalgae problematic to fisheries and toxic to humans and animals. Our study elucidates the molecular mechanisms underlying DA production in the widespread Western Pacific benthic diatom, Nitzschia navis-varingica. Genomic and biochemical insights add information to our understanding of the evolution of toxin production across diverse phyla and also fill a gap in the knowledge of secondary metabolism in marine diatoms. These findings provide a genetic framework for identifying toxin production and its impacts in the benthos of vulnerable, coastal ecosystems.

genomics↗

bioRxiv2024

Discovery and Biosynthesis of Sulfenicin and Its New-to-Nature Acylsulfenic Acid Functional Group

Lifes organic molecules are built with diverse functional groups that enable biology by fine tuning intimate connections through time and space. As such, the discovery of new-to-nature functional groups can expand our understanding of the natural world and motivate new applications in biotechnology and biomedicine. Herein we report the genome-aided discovery of sulfenicin, a novel polyketide-nonribosomal peptide hybrid natural product from a marine Streptomyces bacterium bearing a unique acylsulfenic acid functionality. Through a series of heterologous biosynthesis, functional genetics, and enzymatic reconstitution experiments, we show that this previously described synthetic functional group is biologically assembled by a set of enzymes from both primary and secondary metabolism, including a novel flavin-dependent S-hydroxylase that hydroxylates a thiocarboxylic acids sulfur atom. While the sulfenicin biosynthetic gene cluster is presently without parallel in public databases, acylsulfenic acid-encoding enzymes are widely distributed in bacterial genomes, implying that this labile functional group may similarly have a broad distribution among specialized metabolites.

biochemistry↗

bioRxiv2024

Growth-coupled microbial biosynthesis of the animal pigment xanthommatin

The mining of genomes across life has unearthed a bounty of biosynthetic potential to diverse molecules key to a biobased future. While the heterologous expression of metabolic pathways has achieved broad success, most approaches suffer a similar fate in low initial production levels that require extensive, resource-heavy iterative strain engineering refinement. Herein we introduce a growth-coupled biosynthetic (GrowBio) strategy that irrevocably connects microbial growth with specialized compound production. We demonstrate the plug-and-play versatility of GrowBio in the production of the structurally complex animal biopigment xanthommatin, a color-changing ommochrome with material and cosmetic potential. Xanthommatin biosynthesis directly fuels growth of a newly designed Pseudomonas putida 5,10-methylenetetrahydrofolate auxotroph (PUMA). Aided by genome-scale metabolic modeling, PUMA was designed and built to be controlled by endogenous formate co-produced as a coupled biosynthetic byproduct in the multistep conversion of tryptophan to xanthommatin. Adaptive laboratory evolution was utilized to streamline xanthommatins gram-scale bioproduction via growth rate selection, establishing GrowBio as a promising biotechnological approach for establishing and optimizing the microbial production of value-added molecules.

synthetic biology↗

bioRxiv2024

Giant polyketide synthase enzymes biosynthesize a giant marine polyether biotoxin.

Prymnesium parvum are harmful haptophyte algae that cause massive environmental fish-kills. Their polyketide polyether toxins, the prymnesins, are amongst the largest nonpolymeric compounds in nature, alongside structurally-related health-impacting "red-tide" polyether toxins whose biosynthetic origins have been an enigma for over 40 years. Here we report the PKZILLAs, massive P. parvum polyketide synthase (PKS) genes, whose existence and challenging genomic structure evaded prior detection. PKZILLA-1 and -2 encode giant protein products of 4.7 and 3.2 MDa with 140 and 99 enzyme domains, exceeding the largest known protein titin and all other known PKS systems. Their predicted polyene product matches the proposed pre-prymnesin precursor of the 90-carbon-backbone A-type prymnesins. This discovery establishes a model system for microalgal polyether biosynthesis and expands expectations of genetic and enzymatic size limits in biology.

genomics↗

bioRxiv2023

Molecular Forecasting of Domoic Acid during a Pervasive Toxic Diatom Bloom

In 2015, the largest recorded harmful algal bloom (HAB) occurred in the Northeast Pacific, causing nearly 100 million dollars in damages to fisheries and killing many protected marine mammals. Dominated by the toxic diatom Pseudo-nitzschia australis, this bloom produced high levels of the neurotoxin domoic acid (DA). Through molecular and transcriptional characterization of 52 near-weekly phytoplankton net-tow samples collected at a bloom hotspot in Monterey Bay, California, we identified active transcription of known DA biosynthesis (dab) genes from the three identified toxigenic species, including P. australis as the primary origin of toxicity. Elevated expression of silicon transporters (sit1) during the bloom supports the previously hypothesized role of dissolved silica (Si) exhaustion in contributing to bloom physiology and toxicity. We find that co-expression of the dabA and sit1 genes serves as a robust predictor of DA one week in advance, potentially enabling the forecasting of DA-producing HABs. We additionally present evidence that low levels of iron could have co-limited the diatom population along with low Si. Iron limitation represents a previously unrecognized driver of both toxin production and ecological success of the low iron adapted Pseudo-nitzschia genus during the 2015 bloom, and increasing pervasiveness of iron limitation may fuel the escalating magnitude and frequency of toxic Pseudo-nitzschia blooms globally. Our results advance understanding of bloom physiology underlying toxin production, bloom prediction, and the impact of global change on toxic blooms. SignificancePseudo-nitzschia diatoms form oceanic harmful algal blooms that threaten human health through production of the neurotoxin domoic acid (DA). DA biosynthetic gene expression is hypothesized to control DA production in the environment, yet what regulates expression of these genes is yet to be discovered. In this study, we uncovered expression of DA biosynthesis genes by multiple toxigenic Pseudo-nitzschia species during an economically impactful bloom along the North American West Coast, and identified genes that predict DA in advance of its production. We discovered that iron and silica co-limitation restrained the bloom and likely promoted toxin production. This work suggests that increasing iron limitation due to global change may play a previously unrecognized role in driving bloom frequency and toxicity.

ecology↗

bioRxiv2023

Oxidative rearrangement of tryptophan to indole nitrile by a single diiron enzyme

Nitriles are uncommon in nature and are typically constructed from oximes via the oxidative decarboxylation of amino acid substrates or from the derivatization of carboxylic acids. Here we report a third strategy of nitrile biosynthesis featuring the cyanobacterial nitrile synthase AetD. During the biosynthesis of the eagle-killing neurotoxin, aetokthonotoxin, AetD converts the alanyl side chain of 5,7-dibromo-L-tryptophan to a nitrile. Employing a combination of structural, biochemical, and biophysical techniques, we characterized AetD as a non-heme diiron enzyme that belongs to the emerging Heme Oxygenase-like Diiron Oxidase and Oxygenase (HDO) superfamily. High-resolution crystal structures of AetD together with the identification of catalytically relevant products provide mechanistic insights into how AetD affords this unique transformation that we propose proceeds via an aziridine intermediate. Our work presents a new paradigm for nitrile biogenesis and portrays a substrate binding and metallocofactor assembly mechanism that may be shared among other HDO enzymes.

biochemistry↗

bioRxiv2023

Mechanistic and structural insights into a divergent PLP-dependent L-enduracididine cyclase from a toxic cyanobacterium

Cyclic arginine noncanonical amino acids (ncAAs) are found in several actinobacterial peptide natural products with therapeutically useful antibacterial properties. The preparation of ncAAs like enduracididine and capreomycidine currently takes multiple biosynthetic or chemosynthetic steps, thus limiting the commercial availability and applicability of these cyclic guanidine-containing amino acids. We recently discovered and characterized the biosynthetic pathway of guanitoxin, a potent freshwater cya-nobacterial neurotoxin, that contains an arginine-derived cyclic guanidine phosphate within its highly polar structure. The ncAA L-enduracididine is an early intermediate in guanitoxin biosynthesis and is produced by GntC, a unique pyridoxal-5-phosphate (PLP)-dependent enzyme. GntC catalyzes a cyclodehydration from a stereoselectively {gamma}-hydroxylated L-arginine precursor via a reaction that functionally and mechanistically diverges from previously established actinobacterial cyclic arginine ncAA pathways. Herein, we interrogate L-enduracididine biosynthesis from the cyanobacterium Sphaerospermopsis torques-reginae ITEP-024 using spectroscopic, stable isotope labeling techniques, and X-ray crystal structure-guided site-directed mutagenesis. GntC initially facilitates the reversible deprotonations of the - and {beta}-positions of its substrate prior to catalyzing an irreversible diastereoselective dehydration and subsequent intramolecular cyclization. The comparison of holo- and substrate bound GntC structures and activity assays on sitespecific mutants further identified amino acid residues that contribute to the overall catalytic mechanism. These interdisciplinary efforts at structurally and functionally characterizing GntC enables an improved understanding of how Nature divergently produces cyclic arginine ncAAs and generates additional tools for their biocatalytic production and downstream biological applications.

biochemistry↗

bioRxiv2023

A modular plasmid toolkit applied in marine Proteobacteria reveals functional insights during bacteria-stimulated metamorphosis

A conspicuous roadblock to studying marine bacteria for fundamental research and biotechnology is a lack of modular synthetic biology tools for their genetic manipulation. Here, we applied, and generated new parts for, a modular plasmid toolkit to study marine bacteria in the context of symbioses and host-microbe interactions. To demonstrate the utility of this plasmid system, we genetically manipulated the marine bacterium Pseudoalteromonas luteoviolacea, which stimulates the metamorphosis of the model tubeworm, Hydroides elegans. Using these tools, we quantified constitutive and native promoter expression, developed reporter strains that enable the imaging of host-bacteria interactions, and used CRISPR interference (CRISPRi) to knock down a secondary metabolite and a host-associated gene. We demonstrate the broader utility of this modular system for rapidly creating and iteratively testing genetic tractability by modifying marine bacteria that are known to be associated with diverse host-microbe symbioses. These efforts enabled the successful transformation of twelve marine strains across two Proteobacteria classes, four orders and ten genera. Altogether, the present study demonstrates how synthetic biology strategies enable the investigation of marine microbes and marine host-microbe symbioses with broader implications for environmental restoration and biotechnology.

synthetic biology↗

bioRxiv2022

Extreme genome diversity and cryptic speciation in a harmful algal bloom forming eukaryote

Harmful algal blooms (HABs) of the toxic haptophyte Prymnesium parvum are a recurrent problem in many inland and estuarine waters around the world. Strains of P. parvum vary in the toxins they produce and in other physiological traits associated with HABs, but the genetic basis for this variation is unknown. To investigate genome diversity in this morphospecies, we generated genome assemblies for fifteen phylogenetically and geographically diverse strains of P. parvum including Hi-C guided, near-chromosome level assemblies for two strains. Comparative analysis revealed considerable DNA content variation between strains, ranging from 115 Mbp to 845 Mbp. Strains included haploids, diploids, and polyploids, but not all differences in DNA content were due to variation in genome copy number. Haploid genome size between strains of different chemotypes differed by as much as 243 Mbp. Syntenic and phylogenetic analyses indicate that UTEX 2797, a common laboratory strain from Texas, is a hybrid that retains two phylogenetically distinct haplotypes. Investigation of gene families variably present across strains identified several functional categories associated with metabolism, including candidates for the biosynthesis of toxic metabolites, as well as genome size variation, including recent proliferations of transposable elements. Together, our results indicate that P. parvum is comprised of multiple cryptic species. These genomes provide a robust phylogenetic and genomic framework for investigations into the eco-physiological consequences of the intra- and inter-specific genetic variation present in P. parvum and demonstrate the need for similar resources for other HAB-forming morphospecies. SIGNIFICANCE STATEMENTHarmful algal blooms (HABs) are a global concern. Efforts to understand the genetic basis of traits associated with the success of HAB-forming species are limited by a dearth of genomic resources. In this paper we present genomes for fifteen strains of Prymnesium parvum, a toxic alga that causes ecosystem and societally disruptive HABs around the world. We uncover an unprecedented amount of sequence-level, gene family, and genome architecture evolution in P. parvum and provide evidence for both cryptic speciation and hybridization. These results illustrate how both inter- and intraspecific genetic variation can be dramatically underestimated in a protist morphospecies. More work is needed to understand the eco-physiological consequences of hidden genetic diversity in P. parvum and HAB-forming species more generally.

evolutionary biology↗

bioRxiv2020

Phylogenetic analysis of the salinipostin γ-butyrolactone gene cluster uncovers new potential for bacterial signaling-molecule diversity

Bacteria communicate by small-molecule chemicals that facilitate intra- and inter-species interactions. These extracellular signaling molecules mediate diverse processes including virulence, bioluminescence, biofilm formation, motility, and specialized metabolism. The signaling molecules produced by members of the phylum Actinobacteria are generally comprised of {gamma}-butyrolactones, {gamma}-butenolides, and furans. The best known actinomycete {gamma}-butyrolactone is A-factor, which triggers specialized metabolism and morphological differentiation in the genus Streptomyces. Salinipostins A-K are unique {gamma}-butyrolactone molecules with rare phosphotriester moieties that were recently characterized from the marine actinomycete genus Salinispora. The production of these compounds has been linked to the 9-gene biosynthetic gene cluster spt. Critical to salinipostin assembly is the {gamma}-butyrolactone synthase encoded by spt9. Here, we report the global distribution of spt9 among sequenced bacterial genomes, revealing a surprising diversity of gene homologs across 12 bacterial phyla, the majority of which are not known to produce {gamma}-butyrolactones. Further analyses uncovered a large group of spt-like gene clusters outside of the genus Salinispora, suggesting the production of new salinipostin-like diversity. These gene clusters show evidence of horizontal transfer between many bacterial taxa and location specific homologous recombination exchange among Salinispora strains. The results suggest that {gamma}-butyrolactone production may be more widespread than previously recognized. The identification of new {gamma}-butyrolactone biosynthetic gene clusters is the first step towards understanding the regulatory roles of the encoded small molecules in Actinobacteria. ImportanceSignaling molecules orchestrate a wide variety of bacterial behaviors. Among Actinobacteria, {gamma}-butyrolactones mediate morphological changes and regulate specialized metabolism. Despite their importance, few {gamma}-butyrolactones have been linked to their cognate biosynthetic gene clusters. A new series of {gamma}-butyrolactones called the salinipostins was recently identified from the marine actinomycete genus Salinispora and linked to the spt biosynthetic gene cluster. Here we report the detection of spt-like gene clusters in diverse bacterial families not known for the production of this class of compounds. This finding expands the taxonomic range of bacteria that may employ this class of compounds and provides opportunities to discover new compounds associated with chemical communication.

microbiology↗

bioRxiv2020

Expansion of gamma-butyrolactone signaling molecule biosynthesis to phosphotriester natural products

Bacterial hormones, such as the iconic gamma-butyrolactone A-factor, are essential signaling molecules that regulate diverse physiological processes, including specialized metabolism. These low molecular weight compounds are common in Streptomyces species and display species-specific structural differences. Recently, unusual gamma-butyrolactone natural products called salinipostins were isolated from the marine actinomycete genus Salinispora based on their anti-malarial properties. As the salinipostins possess a rare phosphotriester motif of unknown biosynthetic origin, we set out to explore its construction by the widely conserved 9-gene spt operon in Salinispora species. We show through a series of in vivo and in vitro studies that the spt gene cluster dually encodes the saliniphostins and newly identified A-factor-like gamma-butyrolactones (Sal-GBLs). Remarkably, homologous biosynthetic gene clusters are widely distributed amongst many actinomycete genera, including Streptomyces, suggesting the significance of this operon in bacteria.

biochemistry↗

bioRxiv2020

Co-Occurrence of Enzyme Domains Guides the Discovery of an Oxazolone Synthetase

Multidomain enzymes are cellular machines that orchestrate two or more catalytic activities to carry out metabolic transformations with increased control and speed. Our understanding of these enzymes capabilities drives progress in fundamental metabolic research, biocatalysis, and human health. Here, we report the development of a new genome mining approach for the targeted discovery of novel biochemical transformations through the analysis of co-occurring enzyme domains (CO-ED) in a single protein. CO-ED was designed to identify unannotated multifunctional enzymes for functional characterization and discovery based on the premise that linked enzyme domains have evolved to function collaboratively. Guided by CO-ED, we targeted an unannotated predicted ThiF-nitroreductase di-domain enzyme found in more than 50 proteobacteria. Through heterologous expression and biochemical reconstitution, we discovered a series of new natural products containing the rare oxazolone (azlactone) heterocycle and characterized the di-domain enzyme as the first reported oxazolone synthetase in biology. This enzyme has the potential to become a valuable biocatalyst for the production of versatile oxazolone synthetic intermediates. This proof-of-principle experiment validates CO-ED-guided genome mining as a new method with potential broad utility for both the discovery of novel enzymatic transformations and the functional gene annotation of multidomain enzymes. TOC graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=109 SRC="FIGDIR/small/147165v2_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@20cb16org.highwire.dtl.DTLVardef@f54df0org.highwire.dtl.DTLVardef@cffa51org.highwire.dtl.DTLVardef@3b085d_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2020

Algal Neurotoxin Biosynthesis Repurposes the Terpene Cyclase Structural Fold Into an N-prenyltransferase

Prenylation is a common biological reaction in all domains of life whereupon prenyl diphosphate donors transfer prenyl groups onto small molecules as well as large proteins. The enzymes that catalyze these biotransformations are structurally distinct from ubiquitous terpene cyclases that instead assemble terpene molecules via intramolecular rearrangements. Herein we report the structure and molecular details of a new family of prenyltransferases from marine algae that repurposes the terpene cyclase structural fold for the N-prenylation of glutamic acid during the biosynthesis of the potent neurochemicals domoic acid and kainic acid. We solved the X-ray crystal structure of the prenyltransferase found in domoic acid biosynthesis, DabA, and show distinct active site binding modifications that remodel the canonical Mg2+-binding motif. We then applied our structural knowledge of DabA and a homologous enzyme from the kainic acid biosynthetic pathway, KabA, to alter their isoprene donor specificities (geranyl versus dimethylallyl diphosphate) by a single amino acid switch. While the diatom DabA and seaweed KabA enzymes share a common evolutionary lineage, they are distinct from all other terpene cyclases, suggesting a very distant ancestor. SignificanceDomoic acid is a neurotoxin produced by marine algae that readily bioaccumulates in shellfish and significantly impacts both human and animal life. The first committed step of the biosynthesis of domoic acid is the N-prenylation of L-glutamic acid by the enzyme DabA. By solving the crystal structure of DabA, we demonstrate that this enzyme has repurposed the common terpene cyclase fold to catalyze an extremely unusual reaction, N-prenylation of an unactivated primary amine. Application of these structural insights enabled rational engineering of two N-prenyltransferase enzymes to accept alternative prenyl donors. Ultimately, these results not only expand the scope of reactions catalyzed by a terpene cyclase family member, but will help inform future domoic acid environmental monitoring efforts.

biochemistry↗

bioRxiv2019

Avant-garde assembly-line biosynthesis expands diversity of cyclic lipodepsipeptide products

Modular nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) enzymatic assembly lines are large and dynamic protein machines that generally undergo a linear progression of catalytic cycles via a series of enzymatic domains organized into independent modules. Here we report the heterologous reconstitution and comprehensive characterization of two hybrid NRPS-PKS assembly lines that defy many standard rules of assembly-line biosynthesis to generate a large combinatorial library of cyclic lipodepsipeptide protease inhibitors called thalassospiramides. We generate a series of precise domain-inactivating mutations in thalassospiramide assembly lines and present compelling evidence for an unprecedented biosynthetic model that invokes inter-module substrate activation and tailoring, module skipping, and pass-back chain extension, whereby the ability to pass the growing chain back to a preceding module is flexible and substrate-driven. Expanding bidirectional inter-module domain interactions could represent a viable mechanism for generating chemical diversity without increasing the size of biosynthetic assembly lines and raises new questions regarding our understanding of the structural features of multi-modular megaenzymes.

molecular biology↗