Biology subjects

Moiseenkova-Bell, V.

Publications and source records attributed to Moiseenkova-Bell, V..

3 recordsLinked to original sources

bioRxiv2025

Structures of Nucleotide-Bound Redondovirus Rep Protein Link Conformation and Function

Circular Rep-encoding single-stranded DNA (CRESS-DNA) virus Rep proteins are multidomain enzymes that mediate viral DNA rolling-circle replication. Reps nick viral DNA to expose a 3 end for polymerase extension, provide an NTP-dependent helicase activity for DNA unwinding, and join nicked ends to form circular viral genomes. Here, we present the first structures of a Rep protein from the Redondoviridae family, a newly discovered family of human-associated CRESS-DNA viruses that replicates within the oral protozoan Entamoeba gingivalis. Using cryo-EM, we characterized the hexameric structures of a Redondovirus Rep helicase bound with ATP{gamma}S, representing the initial ATP-bound state, and with ADP, reflecting the protein state after hydrolysis. The ADP state, but not the ATP state of Rep shows a staircase arrangement of DNA-binding loops that plays a central role in current models for SF3 helicase function. Additionally, we determined a head- to-tail dodecameric structure of ATP{gamma}S-bound Rep, in which both the helicase and endonuclease domains are ordered. Conservation of residues involved in stabilizing the dodecamer suggest that this assembly may be functionally relevant for many CRESS-DNA viruses. The positioning of endonuclease domains in the Rep hexamer, combined with our biophysical analyses of Rep oligomerization, provide new insights into Rep function during viral replication.

microbiology↗

bioRxiv2024

CryoEM structure of an MHC-I/TAPBPR peptide bound intermediate reveals the mechanism of antigen proofreading

Class I major histocompatibility complex (MHC-I) proteins play a pivotal role in adaptive immunity by displaying epitopic peptides to CD8+ T cells. The chaperones tapasin and TAPBPR promote the selection of immunogenic antigens from a large pool of intracellular peptides. Interactions of chaperoned MHC-I molecules with incoming peptides are transient in nature, and as a result, the precise antigen proofreading mechanism remains elusive. Here, we leverage a high-fidelity TAPBPR variant and conformationally stabilized MHC-I, to determine the solution structure of the human antigen editing complex bound to a peptide decoy by cryogenic electron microscopy (cryo-EM) at an average resolution of 3.0 [A]. Antigen proofreading is mediated by transient interactions formed between the nascent peptide binding groove with the P2/P3 peptide anchors, where conserved MHC-I residues stabilize incoming peptides through backbone-focused contacts. Finally, using our high-fidelity chaperone, we demonstrate robust peptide exchange on the cell surface across multiple clinically relevant human MHC-I allomorphs. Our work has important ramifications for understanding the selection of immunogenic epitopes for T cell screening and vaccine design applications.

immunology↗

bioRxiv2020

TRPV2 interaction with small molecules and lipids revealed by cryo-EM

Transient receptor potential vanilloid 2 (TRPV2) plays a critical role in a variety of physiological and pathophysiological processes, putting TRPV2 on the list of important drug targets. Yet, specific TRPV2 agonists and antagonists are currently unavailable. Their development requires a precise knowledge of how the currently known non-specific small molecules interact with TRPV2 at the molecular level. Here we present TRPV2 structures in ligand-bound states resolved by cryo-electron microscopy in the presence of 2-aminoethoxydiphenyl borate (2-ABP), 2-APB with doxorubicin (DOXO), and ruthenium red (RR). We identified a novel 2-APB drug binding site between the S5 helix and S4-S5 linker on two adjacent TRPV2 monomers and determined the mechanism of TRPV2 pore block by RR. We also showed that a large organic molecule like DOXO can enter the TRPV2 pore in the presence of 2-APB. Additionally, we discovered a structural lipid bound in a unique position in the "vanilloid pocket", which is absent in the 2-APB-bound state of the channel, allowing us to propose a model for TRPV2 channel gating. Together, this work provides a further understanding of TRPV2 function and a structural framework for the development of TRPV2-specific modulators.

biophysics↗