Biology subjects

Nan, B.

Publications and source records attributed to Nan, B..

18 recordsLinked to original sources

bioRxiv2026

Reprogrammed peptidoglycan elongation reveals plasticity in bacterial growth modes

Most bacteria are enclosed by a peptidoglycan (PG) cell wall that must be expanded for growth. In rod-shaped species, PG elongation is spatially organized in a species-specific manner, occurring either at the cell poles or along the lateral wall. MreB filaments organize the Rod machinery and are typically required for dispersed, nonpolar PG elongation but are dispensable for polar growth. Whether elongation modes are inherently fixed or can be reprogrammed remains unclear. Escherichia coli and Myxococcus xanthus both elongate PG in a dispersed, nonpolar fashion. Here, we show that heterologous expression of M. xanthus MreB in E. coli relocalizes native MreB to the cell poles, thereby redirecting the Rod machinery and PG elongation to polar sites. Moreover, direct targeting of the Rod synthase PBP2 to the poles is sufficient to drive polar PG elongation in E. coli while preserving rod shape. This reprogrammed growth mode bypasses the requirement for MreB filaments, highlighting a plasticity of the Rod system that suggests polar elongation may have emerged through the evolutionary loss of MreB.

microbiology↗

bioRxiv2025

Structural basis of DNA N6-adenine methylation in eukaryotes

As a transcription-associated epigenetic mark abundantly present in many unicellular eukaryotes, DNA N6-adenine methylation (6mA) is maintained by the AMT1 complex. However, the structure-function relationship of the AMT1 complex remains to be fully elucidated. Here, we employ AlphaFold3 (AF3) for de novo structural modeling of the AMT1 complex, complemented by molecular dynamics simulations. Functional relevance of key structural features, especially those of the AMT1 ternary complex with the double-stranded DNA (dsDNA) substrate and the cofactor, are validated by extensive mutagenesis, both in vivo and in vitro. Our analysis reveals the structural basis for DNA substrate recognition, base flipping, and catalysis in this prototypical eukaryotic DNA 6mA-methyltransferase. It also allows us to delineate the reaction pathway for processive methylation involving translocation of the AMT1 complex along the dsDNA. As the active site is conserved across the MT-A70 family of eukaryotic N6-adenine methyltransferases, the structural insight will facilitate rational design of specific inhibitors.

molecular biology↗

bioRxiv2025

Tissue-like structures formed by a bacterium

Bacteria generally form only simple multicellular structures lacking the stable cell-cell connections characteristic of eukaryotic tissues. However, when the antibiotic moenomycin modifies peptidoglycan cell wall synthesis, rod-shaped cells of the Gram-negative bacterium Myxococcus xanthus become spherical, fuse their outer membranes, and assemble into stable, honeycomb-like lattices resembling eukaryotic tissues. These findings raise the intriguing possibility that some tissue-like organization could have evolved from stress-induced responses in bacterial ancestors.

microbiology↗

bioRxiv2025

A novel mechanism for bacterial sporulation based on programmed peptidoglycan degradation

Many bacteria form spores to endure unfavorable conditions. While Firmicutes generate endospores through cell division, sporulation in non-Firmicutes remains less understood. The Gram-negative bacterium Myxococcus xanthus undergoes sporulation through two distinct mechanisms: rapid sporulation triggered by chemical induction and slow sporulation driven by starvation, both occurring independently of cell division. Instead, these processes depend on the complete degradation of the peptidoglycan (PG) cell wall by two lytic transglycosylases (LTGs), LtgA and LtgB. Remarkably, LtgB programs the pace of PG degradation by LtgA during rapid sporulation, ensuring a controlled process that prevents abrupt PG breakdown and the formation of non-resistant pseudospores. In addition to regulation between LTGs, PG degradation is also influenced by its synthesis; cells exhibiting increased muropeptide production often circumvent sporulation. These findings not only reveal novel mechanisms of bacterial sporulation but also shed light on the regulatory network governing PG dynamics.

microbiology↗

bioRxiv2025

A distinct class of eukaryotic demethylases safeguards the positional fidelity of N6-methyladenine (6mA)

DNA N6-methyladenine (6mA) has recently been rediscovered as an epigenetic mark in eukaryotes. Several demethylases responsible for 6mA removal have been identified in multicellular eukaryotes. However, despite the much higher abundance of 6mA in unicellular species, no such enzymes have been reported and the biological significance of 6mA removal in these organisms remain unclear. Here, we identify and functionally characterize DMT3 as a dedicated 6mA demethylase in unicellular eukaryotes. DMT3 targets both fully and hemi-methylated ApT dinucleotides on DNA. It is predominantly localized at transcription start sites (TSS), where it antagonizes the activity of the 6mA methyltransferase AMT1. Deletion or catalytic inactivation of DMT3 leads to genome-wide ectopic 6mA deposition specifically at TSS regions, driven by AMT1, and is accompanied by increased chromatin accessibility and elevated enrichment of transcription-associated histone marks. These epigenetic alterations disrupt gene expression, reduce osmotic stress resistance, and impair the initiation of sexual reproduction. Together, our findings uncover a critical 6mA demethylase in unicellular eukaryotes, and highlight the essential role of active 6mA removal in maintaining transcriptional and developmental integrity.

genetics↗

bioRxiv2025

Impaired envelope integrity in the absence of SanA is linked to increased Lipid II availability and an imbalance of FtsI and FtsW activities

In Gram-negative bacteria, the outer membrane (OM) acts in conjunction with the peptidoglycan (PG) cell wall as a barrier against physical, osmotic, and chemical environmental stressors including antibiotics. SanA, an inner membrane protein in Escherichia coli K-12, is required for vancomycin resistance at high temperatures (>42 {degrees}C) and impacts sodium dodecyl sulfate (SDS) resistance during stationary phase reached from carbon limitation. However, its function remains unknown. Here, we show that {Delta}sanA has a synthetic genetic interaction with {Delta}wecA, a mutation that increases the availability of the isoprenoid carrier for PG synthesis. Specifically, the {Delta}sanA {Delta}wecA strain demonstrated heightened SDS-EDTA sensitivity, activation of the Rcs stress response, and increased cell length. Further investigation tied the SDS-EDTA sensitivity to increased lipid II available for PG synthesis. Spontaneous suppressor mutants of this phenotype harbored point mutations in prc, which encodes tail specific protease, or ftsI, which encodes the cell division DD-transpeptidase, a target of Prc. We focused on the ftsI mutations and demonstrated that the ftsI mutations had increased cell length but nevertheless enhanced PG incorporation at the septum compared to the {Delta}sanA mutant, returning PG incorporation to wild-type levels. Moreover, other mutations affecting septal PG synthesis, but not divisome assembly, also suppressed the SDS-EDTA sensitivity. These findings suggest that, in the absence of SanA, increased lipid II availability perturbs the balance between septal PG synthesis, lateral PG elongation, and other envelope biogenesis pathways, which leads to increased OM permeability. IMPORTANCEThe Gram-negative cell envelope is a barrier that protects the cell from environmental stress. Therefore, the synthesis of each layer of this envelope needs to be closely coordinated throughout growth and division. Here, we investigated SanA, a protein in Escherichia coli K-12 that affects envelope permeability under cellular stress, including nutrient limitation and high temperature. We found that SanA plays a key role in maintaining the permeability barrier when precursor levels for peptidoglycan (PG) synthesis are elevated, linking envelope integrity to balanced septal PG production during cell division. Our results suggest that SanA modulates substrate availability to preserve envelope function, and that in its absence, imbalanced substrate flux to septal PG synthesis disrupts septum formation and compromises barrier integrity.

microbiology↗

bioRxiv2025

Autonomous division of the outer membrane in Gram-negative bacteria

Gram-negative bacteria divide by separating two cell wall layers: peptidoglycan (PG) and the outer membrane (OM). In certain model organisms, the OMs are tethered to PG, ensuring it closely follows PG when cells constrict at division sites. In contrast, the OMs of Myxococcus xanthus exhibit slight invagination at the onset of cell division but do not follow the constriction of PG, instead separating significantly later, only after complete PG fission. However, reinforcing the OM-PG connection by overexpressing tethering proteins, either the endogenous Pal or the exogenous Lpp, synchronizes the constriction of both layers. Our findings suggest that OMs can divide by simple mechanical force. The variability in OM division mechanisms among Gram-negative bacteria reflects differences in both the mode of PG division and the strength of PG-OM interactions.

microbiology↗

bioRxiv2025

Mechanism of bacterial outer membrane exchange revealed by quantitative microscopy

Kin recognition, the ability to distinguish self from nonself at the cellular level is critical to multicellular life. Myxococcus xanthus is a multicellular bacterium that cooperates among genetically-related cells and reduces exploitation by nonkin through outer membrane exchange (OME) of common goods and toxins. The polymorphic cell surface receptor called TraA and its partner protein TraB mediate kin recognition by OME, but its molecular mechanism remains unknown. Here we show that TraAB induce OME by overcoming the repulsive interaction between cells. Using quantitative microscopy techniques, we determined that TraA and TraB form complexes at a 1:1 ratio and that as few as one intercellular TraAB-TraAB dimer is sufficient to induce OME. We visualized the OME of single protein particles between cells and revealed that OME depends on the free diffusion of outer membrane (OM) contents. Our findings suggest a mechanism that shows analogies to the eukaryotic soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), which mediate plasma membrane fusion. M. xanthus OME provides a novel pathway that leads to an underlying conserved mechanism for membrane fusion that is a foundation process for multicellularity.

microbiology↗

bioRxiv2024

Parallel neuroinflammatory pathways to cerebrovascular injury and amyloid-beta in Alzheimer's disease

ImportanceWhile the hallmark pathologies of amyloid-beta (A{beta}) and tau in Alzheimers disease (AD) are well documented and even part of the definition, upstream neuroinflammation is thought to play an important role but remains poorly understood. ObjectivesWe tested whether two distinct neuroinflammatory markers are associated with cerebrovascular injury and A{beta}, and whether these markers are associated with plasma phosphorylated tau (pTau) concentration, medial temporal lobe (MTL) cortical and hippocampal atrophy, and memory deficits. We examined neuroinflammatory markers plasma YKL-40 and GFAP, due to previous conflicting evidence relating YKL-40 and GFAP to AD pathogenic markers. DesignCross-sectional data from a community observational study (Biomarker Exploration in Aging, Cognition, and Neurodegeneration - BEACoN) were included. SettingAll participants were enrolled in a single site, at University of California, Irvine. Participants126 participants were included if they had at least one of the following measures available: neuropsychological data, MRI, A{beta}-PET, or plasma. ExposuresPlasma YKL-40 and plasma glial fibrillary acidic protein (GFAP) levels. Main outcomes and measuresWhite matter hyperintensity (WMH) volume, 18F-florbetapir (FBP) PET mean SUVR, plasma phosphorylated tau (pTau-217) concentration, MTL cortical thickness, hippocampal volume, and memory function assessed by Rey Auditory Verbal Learning Test. Using path analysis, we tested whether higher plasma YKL-40 and GFAP are associated with WMH and A{beta}, and whether these converge to downstream markers of tauopathy, MTL neurodegeneration, and memory deficits. ResultsIn older adults without dementia (N=126, age=70.60+6.29, 62% women), we found that higher plasma YKL-40 concentration was associated with greater WMH volume, while higher plasma GFAP concentration was related to increased FBP SUVR. Further, higher plasma GFAP, WMH and FBP SUVR were independently associated with increased pTau-217. In turn, plasma pTau-217 was associated with reduced MTL cortical thickness and hippocampal volume. Subsequently, only reduced hippocampal volume was related to lower memory function. Conclusions and RelevanceNeuroinflammatory markers contribute to parallel pathways of cerebrovascular injury and A{beta}, which converge to tau-associated neurodegeneration and memory deficits in older adults. These observations underscore the need for a more comprehensive approach to developing an AD framework and treatment strategies. KEY POINTSO_ST_ABSQuestionC_ST_ABSHow does neuroinflammation impact downstream features of cerebrovascular injury and amyloid-beta (A{beta}) in Alzheimers disease? FindingsIn this study of 126 older adults without dementia, we found evidence for two distinct neuroinflammatory pathways that lead to neurodegeneration and memory deficits. One path involves plasma YKL-40 and its impact on cerebrovascular injury, as measured by white matter hyperintensities (WMH) on MRI scans. The other involves plasma glial fibrillary acidic protein (GFAP) and its impact on A{beta} deposition measured via 18F-florbetapir (FBP) PET. Both pathways converged on tauopathy, measured by plasma pTau-217, which was associated with lower medial temporal lobe (MTL) cortical thickness and hippocampal volume, and consequently, memory deficits. MeaningInflammation acts on Alzheimers disease mechanisms via multiple distinct and parallel pathways which converge downstream onto neurodegeneration. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/616579v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@2d3c39org.highwire.dtl.DTLVardef@1ccc453org.highwire.dtl.DTLVardef@6d40bdorg.highwire.dtl.DTLVardef@b543cb_HPS_FORMAT_FIGEXP M_FIG C_FIG Credit: BioRender was used to help create this graphical abstract.

neuroscience↗

bioRxiv2024

Dual modes of DNA N6-methyladenine maintenance by distinct methyltransferase complexes

Stable inheritance of DNA N6-methyladenine (6mA) is crucial for its biological functions in eukaryotes. Here, we identify two distinct methyltransferase (MTase) complexes, both sharing the catalytic subunit AMT1, but featuring AMT6 and AMT7 as their unique components, respectively. While the two complexes are jointly responsible for 6mA maintenance methylation, they exhibit distinct enzymology, DNA/chromatin affinity, genomic distribution, and knockout phenotypes. AMT7 complex, featuring high MTase activity and processivity, is connected to transcription-associated epigenetic marks, including H2A.Z and H3K4me3, and is required for the bulk of maintenance methylation. In contrast, AMT6 complex, with reduced activity and processivity, is recruited to initiate maintenance methylation immediately after DNA replication. These two complexes coordinate in maintenance methylation. By integrating signals from both replication and transcription, this mechanism ensures the faithful and efficient transmission of 6mA as an epigenetic mark in eukaryotes. Significance statementDNA N6-methyladenine (6mA) has recently been recognized as an epigenetic mark in eukaryotes. The stable inheritance of 6mA is essential for its biological functions. However, the precise mechanisms by which 6mA patterns are faithfully and efficiently transmitted remain largely unknown. Here, we have identified two distinct 6mA methyltransferase (MTase) complexes and elucidated their coordinated role in maintenance methylation. This dual- complex mechanism ensures rapid and accurate methylation at newly replicated loci with proper transcription-associated epigenetic marks.

molecular biology↗

bioRxiv2024

A lytic transglycosylase connects bacterial focal adhesion complexes to the peptidoglycan cell wall

The Gram-negative bacterium Myxococcus xanthus glides on solid surfaces. Dynamic bacterial focal adhesion complexes (bFACs) convert proton motive force from the inner membrane into mechanical propulsion on the cell surface. It is unclear how the mechanical force transmits across the rigid peptidoglycan (PG) cell wall. Here we show that AgmT, a highly abundant lytic PG transglycosylase homologous to Escherichia coli MltG, couples bFACs to PG. Coprecipitation assay and single-particle microscopy reveal that the gliding motors fail to connect to PG and thus are unable to assemble into bFACs in the absence of an active AgmT. Heterologous expression of E. coli MltG restores the connection between PG and bFACs and thus rescues gliding motility in the M. xanthus cells that lack AgmT. Our results indicate that bFACs anchor to AgmT-modified PG to transmit mechanical force across the PG cell wall.

microbiology↗

bioRxiv2023

Integrin-like adhesin CglD confers traction and stabilizes bacterial focal adhesions involved in myxobacterial gliding motility

AO_SCPLOWBSTRACTC_SCPLOWIntegrins are crucial for eukaryotic cell attachment and motility within the extracellular matrix (ECM) via focal-adhesion formation, with their evolutionary emergence important for the development of multicellularity. Intriguingly, single gliding cells of the predatory deltaproteobacterium Myxococcus xanthus form bacterial focal-adhesion (bFA) sites; therein, helically-trafficked motors become immobilized at anchored locations through Glt apparatus association with cell-surface integrin I-domain-like adhesin CglB. Using traction-force, bead-force, and total internal reflection-fluorescence microscopies combined with biochemical approaches, we herein identify the von Willebrand A domain-containing cell-surface lipoprotein CglD to be a {beta}-integrin-like outer-membrane lipoprotein that functionally associates with and anchors the trans-envelope Glt-CglB gliding apparatus, stabilizing and efficiently anchoring this assembly at bFAs. Calcium dependence governs CglD importance, consistent with its integrated ECM eukaryotic cartilage oligomeric matrix protein domains. CglD thus confers mechanosensory and mechanotransductory capabilities to the gliding apparatus, helping explain bFA-mediated trans-envelope force transduction, from inner-membrane-embedded motors to the cell surface.

microbiology↗

bioRxiv2023

Semi-conservative transmission of DNA N6-adenine methylation in a unicellular eukaryote

While DNA N6-adenine methylation (6mA) is best known in prokaryotes, its presence in eukaryotes has generated great interest recently. Biochemical and genetic evidence supports that AMT1, a MT-A70 family methyltransferase (MTase), is crucial for 6mA deposition in unicellular eukaryotes. Nonetheless, 6mA transmission mechanism remains to be elucidated. Taking advantage of Single Molecule Real-Time Circular Consensus Sequencing (SMRT CCS), here we provide definitive evidence for semi-conservative transmission of 6mA, showcased in the unicellular eukaryote Tetrahymena thermophila. In wildtype (WT) cells, 6mA occurs at the self-complementary ApT dinucleotide, mostly in full methylation (full-6mApT); hemi-methylation (hemi-6mApT) is transiently present on the parental strand of newly replicated DNA. In {Delta}AMT1 cells, 6mA predominantly occurs as hemi-6mApT. Hemi-to-full conversion in WT cells is fast, robust, and likely processive, while de novo 6mA deposition in {Delta}AMT1 cells is slow and sporadic. In Tetrahymena, regularly spaced 6mA clusters coincide with linker DNA of the canonical nucleosome arrays in the gene body. Importantly, in vitro methylation of human chromatin by reconstituted AMT1 complex recapitulates preferential targeting of hemi-6mApT sites in linker DNA, supporting AMT1s intrinsic and autonomous role in maintenance methylation. We conclude that 6mA is transmitted by a semi-conservative mechanism: full-6mApT is split by DNA replication into hemi-6mApT, which is restored to full-6mApT by AMT1-dependent maintenance methylation. Our study dissects AMT1-dependent maintenance methylation and AMT1-independent de novo methylation, reveals a molecular pathway for 6mA transmission with striking similarity to 5-methyl cytosine (5mC) transmission at the CpG dinucleotide, and establishes 6mA as a bona fide eukaryotic epigenetic mark.

molecular biology↗

bioRxiv2022

Posterior white matter hyperintensities are associated with reduced medial temporal lobe subregional integrity and long-term memory in older adults

White matter hyperintensities are a marker of small vessel cerebrovascular disease that are strongly related to cognition in older adults. Similarly, medial temporal lobe atrophy is well-documented in aging and Alzheimers disease and is associated with memory decline. Here, we assessed the relationship between lobar white matter hyperintensities, medial temporal lobe subregional volumes, and hippocampal memory in older adults. We collected MRI scans in a sample of 139 older adults without dementia (88 females, mean age (SD) = 76.95 (10.61)). Participants were administered the Rey Auditory Verbal Learning Test (RAVLT). Regression analyses tested for associations among medial temporal lobe subregional volumes, regional white matter hyperintensities and memory, while adjusting for age, sex, and education and correcting for multiple comparisons. Increased occipital white matter hyperintensities were related to worse RAVLT delayed recall performance, and to reduced CA1, dentate gyrus, perirhinal cortex (Brodmann area 36), and parahippocampal cortex volumes. These medial temporal lobe subregional volumes were related to delayed recall performance. The association of occipital white matter hyperintensities with delayed recall performance was fully mediated statistically only by perirhinal cortex volume. These results suggest that white matter hyperintensities may be associated with memory decline through their impact on medial temporal lobe atrophy. These findings provide new insights into the role of vascular pathologies in memory loss in older adults and suggest that future studies should further examine the neural mechanisms of these relationships in longitudinal samples.

neuroscience↗

bioRxiv2022

Myxococcus xanthus, a nonpathogenic bacterium, eliminates Cryptococcus neoformans, a fungal pathogen of human, independent of cell-cell contact

Each year an estimated 1.2 billion people suffer from fungal diseases and 1.5 - 2 million die from fungal infections - surpassing the loss from malaria and tuberculosis1-3. Due to the similarities between fungal and human cells, the lack of fungal-specific targets has become the major hurdle for antifungal discovery. Many fungi, including the deadly human pathogen Cryptococcus neoformans, are found in soil, where they compete with other microorganisms, including bacteria. However, most bacteria that inhibit fungal growth are pathogens and their antifungal effects strictly rely on cell-cell contact. Here we show that Myxococcus xanthus, a nonpathogenic, soil-dwelling bacterium, efficiently eliminates C. neoformans and strongly inhibits the production of fungal virulence factors. Remarkably, these antifungal activities do not require cell-cell contact. Using fluorescence microscopy, we found that M. xanthus increases the permeability of C. neoformans cells. Our results on the cross-kingdom interaction between M. xanthus and C. neoformans will reveal fundamental mechanisms for bacterial-fungal interactions and suggest novel strategies for antifungal therapies.

microbiology↗

bioRxiv2022

The coordination between penicillin-binding protein 1a (PBP1a) and the hydrolytic peptidase DacB determines the integrity of bacterial cell poles

Peptidoglycan (PG) defines cell shape and protects bacteria against osmotic stress. The growth and integrity of PG require coordinated actions between synthases that insert new PG strands and hydrolases that generate openings to allow the insertion. However, the mechanisms of their coordination remain elusive. Here we show that moenomycin that inhibits a family of PG synthases known as Class-A penicillin-binding proteins (aPBPs), triggers cell lysis despite aPBPs being non-essential for cell integrity. We demonstrate that inhibited PBP1a2, an aPBP, accelerates the degradation of cell poles by DacB, a hydrolytic PG peptidase, in the bacterium Myxococcus xanthus. Moenomycin reduces the mobility of DacB molecules through PBP1a2, potentially promoting the binding between DacB and PG. Conversely, DacB also regulates the distribution and dynamics of aPBPs. These findings reveal the lethal action of moenomycin and suggest that disrupting the coordination between PG synthases and hydrolases could be more lethal than eliminating individual enzymes.

microbiology↗

bioRxiv2019

Establishing Rod-Shape from Spherical, Peptidoglycan-Deficient Bacterial Spores

Chemical-induced spores of the Gram-negative bacterium Myxococcus xanthus are peptidoglycan (PG)-deficient. It is unclear how these spherical spores germinate into rod-shaped, walled cells without preexisting PG templates. We found that germinating spores first synthesize PG randomly on spherical surfaces. MglB, a GTPase-activating protein, forms a cluster that surveys the status of PG growth and stabilizes at one future cell pole. Following MglB, the Ras family GTPase MglA localizes to the second pole. MglA directs molecular motors to transport the bacterial actin homolog MreB and the Rod PG synthesis complexes away from poles. The Rod system establishes rod-shape by elongating PG at nonpolar regions. Thus, the interaction between GTPase, cytoskeletons and molecular motors provides a mechanism for the de novo establishment of rod-shape in bacteria. SignificanceSpheres and rods are among the most common shapes adopted by walled bacteria, in which the peptidoglycan (PG) cell wall largely determines cell shape. When induced by chemicals, rod-shaped vegetative cells of the Gram-negative bacterium Myxococcus xanthus thoroughly degrade their PG and shrink into spherical spores. As these spores germinate, rod-shaped cells are rebuilt without preexisting templates, which provides a rare opportunity to visualize de novo PG synthesis and bacterial morphogenesis. In this study, we investigated how spherical spores germinate into rods and elucidated a system for rod-shape morphogenesis that includes the Rod PG synthesis system, a GTPase-GAP pair, the MreB cytoskeleton and a molecular motor.

microbiology↗

bioRxiv2019

Second messengers and divergent HD-GYP enzymes regulate 3’,3’-cGAMP signaling

3,3-cyclic GMP-AMP (cGAMP) is the third cyclic dinucleotide (CDN) to be discovered in bacteria. No activators of cGAMP signaling have yet been identified, and the signaling pathways for cGAMP have appeared narrowly distributed based upon the characterized synthases, DncV and Hypr GGDEFs. Here we report that the ubiquitous second messenger cyclic AMP (cAMP) is an activator of the Hypr GGDEF enzyme GacB from Myxococcus xanthus. Furthermore, we show that GacB is inhibited directly by cyclic di-GMP, which provides evidence for cross-regulation between different CDN pathways. Finally, we reveal that the HD-GYP enzyme PmxA is a cGAMP-specific phosphodiesterase (GAP) that promotes resistance to osmotic stress in M. xanthus. A signature amino acid change in PmxA was found to reprogram substrate specificity and was applied to predict the presence of non-canonical HD-GYP phosphodiesterases in many bacterial species, including phyla previously not known to utilize cGAMP signaling.

biochemistry↗