Biology subjects

Bethel, N. P.

Publications and source records attributed to Bethel, N. P..

8 recordsLinked to original sources

bioRxiv2026

Optimization of the NFκB-DNA ensemble leads to high affinity binding of partial consensus sites

Our ability to respond to a myriad of external stressors is dependent on the activity of specific transcription factors that precisely regulate gene expression. While some transcription factors have high specificity for their consensus DNA binding site, others such as NF{kappa}B (RelA/p50) readily bind to partial and nonconsensus sites. In fact, ChIP-Seq data shows that nearly half of the DNA-bound RelA occupies sequences that do not match the consensus. Here we explore how NF{kappa}B (RelA/p50) binds to alternative sequences that differ subtly from the consensus. The two subunits of the NF{kappa}B heterodimer, RelA and p50, form an extensive pocket where DNA binding is mediated by both base-specific contacts and nonspecific interactions with the DNA backbone. RelA and p50 each form sequence-specific contacts with DNA at different 4-nucleotide sequences separated by two nucleotides, together forming a 10-base pair consensus binding sequence. Partial consensus sequences, known as half-sites, match the consensus sequence at only one of these two 4-nucleotide interaction sites. Here, using hydrogen deuterium exchange mass spectrometry (HDX-MS) and molecular dynamics (MD) simulations to investigate protein structural dynamics, we observe that rearranging nucleotides at the RelA-interacting end of a consensus DNA sequence to form a half-site induces dynamic structural changes through both subunits of RelA/p50. MD simulations reveal a shift in the position of DNA within the RelA/p50 binding pocket that allows optimal interaction with the half-site sequence. Our results demonstrate how RelA/p50 fine-tunes its interactions to achieve high-affinity binding with multiple different target DNA sequences.

biochemistry↗

bioRxiv2026

Programmable De Novo Design of Mesoporous Protein Crystal Frameworks

Three-dimensional protein crystals are ordered, porous macroscopic materials with potential applications in catalysis, biosensing, and biomedicine. However, most protein crystals are obtained by empirical screening, providing limited control over the lattice architecture, pore geometry or component composition that determine material function. Here, we present a modular strategy for the programmable design of highly porous, framework-like protein crystals using predefined protein-protein interactions. This strategy yielded over 30 distinct protein crystals, including single-component and multicomponent P213 and I213 lattices that grow to over 100 micrometers in size. Small-angle X-ray scattering and electron microscopy showed close agreement between experimental lattices and computational models. RFdiffusion-guided design generated isomorphous variants with matched lattice parameters, enabling coherent protein crystal alloys, epitaxial core-shell growth and reversible shell assembly. The designed crystals exhibit tunable mesoporous architectures, with limiting apertures of 2-18 nm, and support genetically encoded incorporation of fluorescent protein guests. These results establish a general route to programmable lattice engineering of protein crystals and position them as genetically encoded, compositionally tunable mesoporous materials.

synthetic biology↗

bioRxiv2026

Templating and confining calcium phosphate mineralization within designed protein assemblies

Bone formation involves the deposition of ordered hydroxyapatite (HAp) on collagen fibrils, but the underlying molecular mechanisms remain largely unresolved, limiting the design of protein-apatite hybrid materials. Here we show that computationally designed de novo proteins can template and confine HAp mineralization. We design C3-symmetric oligomers with inner surfaces chemically complementary to the HAp {010} facet, and assemble these through additional interfaces into D3 oligomers, one-dimensional nanotubes, and two-dimensional arrays. Electron microscopy revealed templated mineralization and confinement at each hierarchical level, with mineral shape guided by the underlying protein architecture. Conversion of an initially formed amorphous phase to HAp is driven by the designed protein-mineral interface. Our results establish a framework for programmable protein-guided mineralization, providing a foundation for next-generation hybrid materials.

biochemistry↗

bioRxiv2025

Inferring Local Protein Structural Similarity from Sequence Alone

Detecting structural similarity at the local level between proteins is central to understanding function and evolution, yet most approaches require 3D models. In this work, we show that protein language models (pLMs), solely using sequence data as input, implicitly capture fine-grained structural signals that can be leveraged to identify such similarities. By mean-pooling residue embeddings over sliding windows and comparing them across proteins with cosine similarity, we find diagonal patterns that reflect locally aligned regions even without sequence identity. Building on this insight, we introduce a framework for detecting locally aligned structural regions directly from sequences, supporting the development of scalable methods for structural annotation and comparison.

bioinformatics↗

bioRxiv2025

RemoteFoldSet: Benchmarking Structural Awareness of Protein Language Models

Protein language models (pLMs) have the capacity to infer structural information from amino acid sequences. Evaluating the extent to which structural information they truly encode is crucial for assessing their generalizability and the interpretability of their latent representations, yet current approaches lack a model-free, quantitative framework to evaluate these encodings. We introduce RemoteFoldSet, a curated collection of protein sequence sets stratified by high structural similarity but minimal sequence identity. We also define the Structural Awareness (SA) score, a novel metric that enables model-agnostic, unsupervised, and training-free quantification of structure-related patterns in pLM embeddings. Using RemoteFoldSet together with the SA score, we benchmark a range of existing pLMs, elucidating how models with different training objectives, architectures, and sizes discriminate and distribute proteins within their embedding spaces, both quantitatively and qualitatively. We expect that this methodology will serve as a reliable benchmark for evaluating the performance of pLMs for structural and functional applications.

biochemistry↗

bioRxiv2023

Local structural flexibility drives oligomorphism in computationally designed protein assemblies

Many naturally occurring protein assemblies have dynamic structures that allow them to perform specialized functions. For example, clathrin coats adopt a wide variety of architectures to adapt to vesicular cargos of various sizes. Although computational methods for designing novel self-assembling proteins have advanced substantially over the past decade, most existing methods focus on designing static structures with high accuracy. Here we characterize the structures of three distinct computationally designed protein assemblies that each form multiple unanticipated architectures, and identify flexibility in specific regions of the subunits of each assembly as the source of structural diversity. Cryo-EM single-particle reconstructions and native mass spectrometry showed that only two distinct architectures were observed in two of the three cases, while we obtained six cryo-EM reconstructions that likely represent a subset of the architectures present in solution in the third case. Structural modeling and molecular dynamics simulations indicated that the surprising observation of a defined range of architectures, instead of non-specific aggregation, can be explained by constrained flexibility within the building blocks. Our results suggest that deliberate use of structural flexibility as a design principle will allow exploration of previously inaccessible structural and functional space in designed protein assemblies.

bioengineering↗

bioRxiv2022

Precisely patterned nanofibers made from extendable protein multiplexes

Molecular systems with coincident cyclic and superhelical symmetry axes have considerable advantages for materials design as they can be readily lengthened or shortened by changing the length of the constituent monomers. Among proteins, alpha helical coiled coils have such symmetric extendable architectures, but are limited by the relatively fixed geometry and flexibility of the helical protomers. Here, we describe a systematic approach to generating modular and rigid repeat protein oligomers with coincident C2 to C8 and superhelical symmetry axes that can be readily extended by repeat propagation. From these building blocks, we demonstrate that a wide range of unbounded fibers can be systematically designed by introducing hydrophilic surface patches that force staggering of the monomers; the geometry of such fibers can be precisely tuned by varying the number of repeat units in the monomer and the placement of the hydrophilic patches.

bioengineering↗

bioRxiv2021

Natural and designed proteins inspired by extremotolerant organisms can form condensates and attenuate apoptosis in human cells

Many organisms can survive extreme conditions and successfully recover to normal life. This extremotolerant behavior has been attributed in part to repetitive, amphipathic, and intrinsically disordered proteins that are upregulated in the protected state. Here, we assemble a library of approximately 300 naturally-occurring and designed extremotolerance-associated proteins to assess their ability to protect human cells from chemically-induced apoptosis. We show that several proteins from tardigrades, nematodes, and the Chinese giant salamander are apoptosis protective. Notably, we identify a region of the human ApoE protein with similarity to extremotolerance-associated proteins that also protects against apoptosis. This region mirrors the phase separation behavior seen with such proteins, like the tardigrade protein CAHS2. Moreover, we identify a synthetic protein, DHR81, that shares this combination of elevated phase separation propensity and apoptosis protection. Finally, we demonstrate that driving protective proteins into the condensate state increases apoptosis protection, and highlight the ability for DHR81 condensates to sequester caspase-7. Taken together, this work draws a link between extremotolerance-associated proteins, condensate formation, and designing human cellular protection.

synthetic biology↗