Carla Calvó-Tusell

Chiral enones are valuable motifs in synthetic intermediates and bioactive molecules, driving significant interest in biocatalysis. Although recent enzymatic desaturation strategies for substituted cyclohexenones provide efficient and highly enantioselective synthetic routes, none offer complementary stereoselectivity. To address this gap, we introduce a stereocomplementary biocatalytic system based on an old yellow enzyme (OYE), XenA from Pseudomonas putida . Although XenA natively catalyzes the reduction of electron‐deficient alkenes and exhibits negligible desaturation activity, protein engineering redirected its catalytic function toward desaturation, ultimately yielding a variant that accommodates a range of cyclohexanones with 85%–99% ee and 32%–98% yield. Remarkably, the optimal variant (XenA_4) possesses 46 mutations and exhibits an 11°C increase in melting temperature over the wild type. Mechanistic studies revealed that the unique dimeric structure of the enzyme is pivotal in controlling stereoselectivity by modulating the substrate‐binding orientation.

Chiral enones are valuable motifs in synthetic intermediates and bioactive molecules, driving significant interest in biocatalysis. Although recent enzymatic desaturation strategies for substituted cyclohexenones provide efficient and highly enantioselective synthetic routes, none offer complementary stereoselectivity. To address this gap, we introduce a stereocomplementary biocatalytic system based on an old yellow enzyme (OYE), XenA from Pseudomonas putida . Although XenA natively catalyzes the reduction of electron‐deficient alkenes and exhibits negligible desaturation activity, protein engineering redirected its catalytic function toward desaturation, ultimately yielding a variant that accommodates a range of cyclohexanones with 85%–99% ee and 32%–98% yield. Remarkably, the optimal variant (XenA_4) possesses 46 mutations and exhibits an 11°C increase in melting temperature over the wild type. Mechanistic studies revealed that the unique dimeric structure of the enzyme is pivotal in controlling stereoselectivity by modulating the substrate‐binding orientation.

The severe acute respiratory syndrome coronavirus 2 spike glycoprotein enables infection through a key conformational transition that exposes its receptor binding domain (RBD). Experimental evidence indicates that spike mutations, particularly the early D614G variant, alter the rate of this conformational shift, potentially increasing viral infectivity. We conducted extensive weighted ensemble simulations of the Ancestral, Delta, and Omicron BA.1 spike strains to investigate relationships between sequence mutations and RBD opening dynamics. We observe that Ancestral, Delta, and Omicron BA.1 spike RBDs open differently. Via dynamical network analysis, we identified two allosteric communication networks connecting all S1 domains: the established N2R linker and a newly investigated antiparallel R2N linker. In Delta and Omicron BA.1 variant spikes, RBD opening is facilitated by both linkers, while the Ancestral strain relies predominantly on the N2R linker. In the Ancestral spike, the D614-K854 salt bridge impedes allosteric communication through the R2N linker, whereas the loss of this salt bridge in all subsequent variants of concerns allows for increased local flexibility, thereby accelerating RBD opening. Hydrogen–deuterium mass spectrometry experiments validate these altered dynamics in the D614 region. This study unveils a “hidden” network, connecting the N-terminal domain to the RBD via the 614-proximal region, and the D614G mutation reshapes the fitness landscape of these critical viral glycoproteins.

The molecular behavior of viruses within respiratory aerosols plays a critical role in airborne disease transmission yet remains largely inaccessible to experimental characterization. Here, we use a billion-atom all-atom molecular dynamics simulation of a virus-laden respiratory aerosol to uncover how respiratory proteins, lipids, ions, and water collectively assemble around SARS-CoV-2, giving rise to structured microenvironments that influence viral stability and spike dynamics. We find that respiratory components rapidly evolve into heterogeneous networks characterized by protein-rich aggregates, patchy lipid assemblies, and spatially structured ion and water dynamics. These features create distinct microenvironments that constrain molecular transport and stabilize regions surrounding the virion. Within this crowded aerosol context, we observe sustained and selective interactions between aerosol components and the viral spike protein, including preferential recruitment of surfactant lipids and persistent coordination by divalent cations. These interactions modulate spike conformational dynamics, enhancing domain breathing motions and flexibility at key hinge regions while preserving a stable membrane anchor. Together, these observations reveal a condensate-like physical regime in which multivalent aerosol components coalesce into a soft, heterogeneous matrix that selectively modulates viral protein dynamics under extreme crowding. By framing virus-laden respiratory aerosols within this physical context, this work establishes an in situ molecular framework for understanding how aerosols influence viral persistence and offers a platform for exploring mechanisms relevant to airborne disease transmission and mitigation strategies.

SARS-like bat coronaviruses (CoVs) pose ongoing public health risks due to their zoonotic potential, making it important to understand the molecular pathways driving their evolution. We recently showed that SHC014-CoV can infect human cell lines in an ACE2-dependent manner after acquiring two spike ectodomain mutations (F294L and A835D). However, how the wild-type (WT) SHC014 spike differs dynamically from these mutants remains unclear. Here, we built fully glycosylated ectodomain models of WT and three mutants (F294L, A835D, and the double mutant, DM) and performed triplicate 1-μs all-atom molecular dynamics (MD) simulations for each variant. The two mutations exhibit epistasis, altering structural rearrangements relative to WT. Notably, the DM receptor binding domain (RBD) begins sampling the open conformation in our conventional MD. At the atomic level, the DM spike mitigates the dense negative packing introduced by A835D through a salt-bridge network, while F294L disrupts π-mediated interactions, together enhancing RBD opening propensity—critical for viral entry. Increased flexibility of the subdomain-2 “620-loop” further modulates DM RBD openness. Dynamical network analysis identified three allosteric communication pathways. In WT and F294L, “Pathway 1” forms the baseline route linking the 620-loop to the RBD, whereas in A835D and DM it extends to the FPPR, reshaping long-range communication. “Pathway 2” is conserved across variants but is most prominent in WT and F294L. “Pathway 3” appears only in A835D and DM, compensating for reduced communication along Pathway 2. Overall, this work provides an atomistic perspective on SHC014 molecular adaptation during host-to-host transmission and highlights mechanistic features that may inform future therapeutic and pandemic-preparedness efforts. Statement of Significance: Bat coronaviruses are an important source of future pandemic threats, but we still know little about how small genetic changes help them infect humans. In this study, we used detailed computer simulations to watch how tiny mutations in a bat coronavirus spike protein change its motion and shape. We found that two specific mutations work together to make the spike more likely to open—a step required for the virus to enter human cells. By revealing how these molecular changes increase infection potential, our work helps improve understanding of coronavirus evolution and may guide strategies to prepare for future outbreaks.

The soluble epoxide hydrolase (sEH) has recently emerged as a promising target for the treatment of several pain-related conditions. Herein, we report the design and synthesis of a peripherally restricted sEH inhibitor with high potency and good Drug Metabolism and Pharmacokinetics (DMPK) properties. Molecular dynamics and X-ray crystallography helped reveal the binding of these inhibitors to sEH. The selected compound showed a robust analgesic effect in a dose-dependent manner in a murine model of chemotherapy-induced neuropathic pain (CINP). Moreover, the compound also prevented the development of paclitaxel-induced neuropathic pain. Overall, these results suggest that peripheral inhibition of sEH might constitute a novel therapy to prevent and treat CINP.

Terminal alkyne-containing natural products can undergo the bio-orthogonal ‘click’ reaction of Cu(I)-catalyzed azide–alkyne cycloaddition. Recently, an enzymatic mechanism for terminal alkyne formation was discovered in the biosynthesis of l-β-ethynylserine where the pyridoxal phosphate-dependent enzyme BesB forms a rare terminal alkyne-containing amino acid, l-propargylglycine, from a vinyl halide precursor, 4-chloro-l-allylglycine. Here we present the 1.3-Å-resolution crystal structure of BesB with detailed mechanistic and computational studies. We demonstrate that BesB can reversibly catalyze the exchange of the halogen in various 4-halo-allyl-l-glycines, implying the existence of an allene intermediate, which we then also observe. Taken together, this work supports a mechanism whereby an allene is formed from deprotonation-driven halogen loss and the terminal alkyne is then formed by isomerization of the allene. Our work further expands our understanding of the catalytic repertoire of pyridoxal phosphate-dependent enzymes and will enable development of metal-free allene-forming and alkyne-forming biocatalysts.

Engineered recombinant Spike (S) has been invaluable for determining S structure and dynamics and is the basis for the design of most prevalent vaccines. While these vaccines have been highly efficacious for short-term protection from infection, protection waned with the emergence of variants (alpha through omicron). Here we report differences in conformational dynamics between native, membrane-embedded full-length S and recombinant S. Our virus-like particle (VLP) model mimics the native SARS CoV-2 virion by displaying S assembled with auxiliary E, M, and N proteins in a native membrane environment that captures the entirety of quaternary interactions mediated by S. Display of S on VLP obviates the requirement for stabilizing modifications that have been engineered into recombinant S for enhanced expression and solubility. Amide hydrogen/deuterium exchange mass spectrometry (HDXMS) reveals altered interprotomer contacts in VLP S trimers attributable to the presence of auxiliary proteins, membrane anchoring, and lack of engineered modifications. Our results reveal decreased dynamics in the S2 subunit and at sites spanning interprotomer contacts in VLP S with minimal differences in the N-terminal domain (NTD) and receptor binding domain (RBD). This carries implications for display of epitopes beyond NTD and RBD. In summary, despite affording efficient structural characterization, recombinant S distorts the intrinsic conformational ensemble of native S displayed on the virus surface.

APOBEC3B (A3B) is implicated in DNA mutations that facilitate tumor evolution. Although structures of its individual N- and C-terminal domains (NTD and CTD) have been resolved through X-ray crystallography, the full-length A3B (fl-A3B) structure remains elusive, limiting understanding of its dynamics and mechanisms. In particular, the APOBEC3B C-terminal domain (A3Bctd) active site is frequently closed in models and structures. In this study, we built several new models of fl-A3B using integrative structural biology methods and selected a top model for further dynamical investigation. We compared dynamics of the truncated (A3Bctd) to the fl-A3B via conventional and Gaussian accelerated molecular dynamics (MD) simulations. Subsequently, we employed weighted ensemble methods to explore the fl-A3B active site opening mechanism, finding that interactions at the NTD-CTD interface enhance the opening frequency of the fl-A3B active site. Our findings shed light on the structural dynamics of fl-A3B, which may offer new avenues for therapeutic intervention in cancer.