Biology subjects

Laughlin, Z. T.

Publications and source records attributed to Laughlin, Z. T..

4 recordsLinked to original sources

bioRxiv2024

Structural basis of SARS-Cov-2 spike recognition by engineered synthetic multivalent VHH antibodies

High-throughput technologies such as next-generation sequencing (NGS), microarray-based gene synthesis, and phage display have empowered the discovery and engineering of precisely defined, synthetic antibodies with high avidity and drug-like features. Here, we describe a scalable process for engineering homo- and hetero-hexavalent variable domains of camelid heavy-chain (VHH)-Fc antibodies against the severe acute respiratory coronavirus 2 (SARS-CoV-2) spike (S) protein. Overall, we demonstrate that VHH trimerization is an effective and modular approach for increasing the affinity of anti-S1 VHH-Fc antibodies for the highly mutated S proteins of SARS-CoV-2 variants. We show that one specific nanobody (named TB201-1) binds spike trimer protein at the interface of two neighboring RBDs, recognizing one distinct epitope on one RBD but making a set of secondary interactions with the neighboring RBD. From this structure, we determine the epitope-paratope residues responsible for spike-nanobody interaction and how mutations found in the SARS-CoV-2 variants contribute to oblate TB201-1 binding. This approach could be leveraged to improve existing antibody-based diagnostics and therapeutics targeting SARS-CoV-2 as the virus evolves.

bioengineering↗

bioRxiv2024

Transgressive Hybrids as Hopeful Holobionts

BackgroundHybridization between evolutionary lineages has profound impacts on the fitness and ecology of hybrid progeny. In extreme cases, the effects of hybridization can transcend ecological timescales by introducing trait novelty upon which evolution can act. Indeed, hybridization can even have macroevolutionary consequences, for example, as a driver of adaptive radiations and evolutionary innovations. Accordingly, hybridization is now recognized as a motor for macrobial evolution. By contrast, there has been substantially less progress made towards understanding the positive eco-evolutionary consequences of hybridization on holobionts. Rather, the emerging paradigm in holobiont literature is that hybridization disrupts symbiosis between a host lineage and its microbiota, leaving hybrids at a fitness deficit. These conclusions, however, have been drawn based on results from predominantly low-fitness hybrid organisms. Studying dead-end hybrids all but guarantees finding that hybridization is detrimental. This is the pitfall that Dobzhansky fell into over 80 years ago when he used hybrid sterility and inviability to conclude that hybridization hinders evolution. Goldschmidt, however, argued that rare saltational successes--so-called hopeful monsters--disproportionately drive positive evolutionary outcomes. Goldschmidts view is now becoming a widely accepted explanation for the prevalence of historical hybridization in extant macrobial lineages. Aligning holobiont research with this broader evolutionary perspective requires recognizing the importance of similar patterns in host-microbiome systems. That is, rare and successful hopeful holobionts (i.e., hopeful monsters at the holobiont scale) might be disproportionately responsible for holobiont evolution. If true, then it is these successful systems that we should be studying to assess impacts of hybridization on the macroevolutionary trajectories of host- microbiome symbioses. ResultsIn this paper, we explore the effects of hybridization on the gut (cloacal) and skin microbiota in an ecologically successful hybrid lizard, Aspidoscelis neomexicanus. Specifically, we test the hypothesis that hybrid lizards have host-associated (HA) microbiota traits strongly differentiated from their progenitor species. Across numerous hybrid microbiota phenotypes, we find widespread evidence of transgressive segregation. Further, microbiota restructuring broadly correlates with niche restructuring during hybridization. This suggests a relationship between HA microbiota traits and ecological success. ConclusionTransgressive segregation of HA microbiota traits is not limited to hybrids at a fitness deficit but also occurs in ecologically successful hybrids. This suggests that hybridization may be a mechanism for generating novel and potentially beneficial holobiont phenotypes. Supporting such a conclusion, the correlations that we find between hybrid microbiota and the hybrid niche indicate that hybridization might change host microbiota in ways that promote a shift or an expansion in host niche space. If true, hybrid microbiota restructuring may underly ecological release from progenitors. This, in turn, could drive evolutionary diversification. Using our system as an example, we elaborate on the evolutionary implications of host hybridization within the context of holobiont theory and then outline the next steps for understanding the role of hybridization in holobiont research.

evolutionary biology↗

bioRxiv2023

A portable and wind resistant drift fence array for arid environments

AbstractDrift fences are passive trapping systems for both small vertebrates and large invertebrates. Most drift fence designs are semi-permanent or otherwise difficult to transport after initial installation. While these designs are effective for replicate trapping through time, most designs lack portability. Here, we propose a novel drift fence design that uses PVC pipes and fiberglass mesh screen. The combination of hollow PVC pipes and mesh screen creates a lightweight system that facilitates rapid deployment and redeployment across locations. Since the PVC pipes can be filled with topsoil from the site of trap installation, enhanced portability does not come at the cost of fence stability or wind resistance. We provide results on trap performance in a New Mexico flatland desert and discuss the efficacy and cost of our proposed drift fence design.

ecology↗

bioRxiv2021

50S subunit recognition and modification by the Mycobacterium tuberculosis ribosomal RNA methyltransferase TlyA

Changes in bacterial ribosomal RNA methylation status can alter the activity of diverse groups of ribosome-targeting antibiotics. These modifications are typically incorporated by a single methyltransferase that acts on one nucleotide target and rRNA methylation directly prevents drug binding, thereby conferring drug resistance. Loss of intrinsic methylation can also result in antibiotic resistance. For example, Mycobacterium tuberculosis becomes sensitized to tuberactinomycin antibiotics, such as capreomycin and viomycin, due to the action of the intrinsic methyltransferase TlyA. TlyA is unique among antibiotic resistance-associated methyltransferases as it has dual 16S and 23S rRNA substrate specificity and can incorporate cytidine-2-O-methylations within two structurally distinct contexts. Here, we report the structure of a mycobacterial 50S subunit-TlyA complex trapped in a post-catalytic state with a S-adenosyl-L-methionine analog using single-particle cryogenic electron microscopy. Together with complementary functional analyses, this structure reveals critical roles in 23S rRNA substrate recognition for conserved residues across an interaction surface that spans both TlyA domains. These interactions position the TlyA active site over the target nucleotide C2144 which is flipped from 23S Helix 69 in a process stabilized by stacking of TlyA residue Phe157 on the adjacent A2143. Base flipping may thus be a common strategy among rRNA methyltransferase enzymes even in cases where the target site is accessible without such structural reorganization. Finally, functional studies with 30S subunit suggest that the same TlyA interaction surface is employed to recognize this second substrate, but with distinct dependencies on essential conserved residues. Significance StatementThe bacterial ribosome is an important target for antibiotics used to treat infection. However, resistance to these essential drugs can arise through changes in ribosomal RNA (rRNA) modification patterns through the action of intrinsic or acquired rRNA methyltransferase enzymes. How these antibiotic resistance-associated enzymes recognize their ribosomal targets for site-specific modification is currently not well defined. Here, we uncover the molecular basis for large ribosomal (50S) subunit substrate recognition and modification by the Mycobacterium tuberculosis methyltransferase TlyA, necessary for optimal activity of the antitubercular drug capreomycin. From this work, recognition of complex rRNA structures distant from the site of modification and "flipping" of the target nucleotide base both emerge as general themes in ribosome recognition for bacterial rRNA modifying enzymes.

biochemistry↗