Biology subjects

Voisin, T. B.

Publications and source records attributed to Voisin, T. B..

5 recordsLinked to original sources

bioRxiv2026

Selective binders of a cotranslational folding intermediate

Drug discovery efforts typically target mature, folded proteins, primarily to inhibit their function or induce their degradation. An alternative strategy would be to target incompletely folded states that are transiently populated during protein biogenesis, but whether these states contain druggable pockets was unclear. Here, we used an mRNA display approach to discover cyclic peptides that recognize a nascent polypeptide at an intermediate point during its synthesis on the ribosome. We identified peptides that bind with low-nanomolar affinity to a model nascent protein, {beta}-galactosidase, but do not detectably bind either the fully-folded protein or ribosomes synthesising different sequences. Hydrogen/deuterium exchange-mass spectrometry and cryogenic electron microscopy revealed the molecular basis for selective binding. We found that the nascent chain folds into an -helix against the ribosome surface during ongoing translation, creating a cryptic pocket together with ribosomal proteins uL23 and uL29 that is exploited by the hit peptides. Our results establish proof-of-concept for selective targeting of protein biogenesis intermediates, and provide a platform for future drug development.

biochemistry↗

bioRxiv2026

Molecular determinants of cotranslational chaperone recruitment to nascent p53

Protein folding is fast relative to mRNA translation and nascent polypeptides begin to fold during their synthesis on the ribosome. The resulting cotranslational folding intermediates are accessible to diverse molecular chaperones that recognise incompletely folded client proteins. Here, we sought to understand how specific chaperone:client complexes are established during protein synthesis, using the chaperone-dependent tumor suppressor protein p53 as a model. By capturing interactomes at different points during p53 synthesis, we show that Hsp70, Hsp90 and TRiC bind competitively to nascent p53. While Hsp70 and Hsp90 bind promiscuously, TRiC discriminates between subtly different partially-folded states. TRiC recruitment is dictated by local cotranslational folding and exposure of specific sequence motifs, and this is tuned by cancer-associated mutations in the p53 DNA-binding domain. Nascent chain interactions with the ribosome surface disfavor TRiC binding, demonstrating that the ribosome imposes unique constraints on chaperone recruitment during protein synthesis. Our results establish molecular principles underlying chaperone prioritization during protein biogenesis.

biochemistry↗

bioRxiv2024

The human ribosome modulates multidomain protein biogenesis by delaying cotranslational domain docking

Proteins with multiple domains are intrinsically prone to misfold, yet fold efficiently during their synthesis on the ribosome. This is especially important in eukaryotes, where multidomain proteins predominate. Here, we sought to understand how multidomain protein folding is modulated by the eukaryotic ribosome. We used cryo-electron microscopy and hydrogen/deuterium exchange-mass spectrometry to characterise the structure and dynamics of partially-synthesised intermediates of a model multidomain protein. We find that nascent subdomains fold progressively during synthesis on the human ribosome, templated by interactions across domain interfaces. The conformational ensemble of the nascent chain is tuned by its unstructured C-terminal segments, which keep interfaces between folded domains in dynamic equilibrium until translation termination. This contrasts with the bacterial ribosome, on which domain interfaces form early and remain stable during synthesis. Delayed domain docking may avoid interdomain misfolding to promote the maturation of multidomain proteins in eukaryotes.

biochemistry↗

bioRxiv2022

Structural basis for membrane attack complex inhibition by CD59

CD59 is an abundant immuno-regulatory receptor that protects human cells from damage during complement activation. Here we show how the receptor binds complement proteins C8 and C9 at the membrane to prevent insertion and polymerization of membrane attack complex (MAC) pores. We present cryoelectron microscopy structures of two inhibited MAC precursors known as C5b8 and C5b9. We discover that in both complexes, CD59 binds the pore-forming {square}-hairpins of C8 to form an intermolecular {square}-sheet that prevents membrane perforation. While bound to C8, CD59 deflects the cascading C9 {square}-hairpins, rerouting their trajectory into the membrane. Preventing insertion of C9 restricts structural transitions of subsequent monomers and indirectly halts MAC polymerization. We combine our structural data with cellular assays and molecular dynamics simulations to explain how the membrane environment impacts the dual roles of CD59 in controlling pore formation of MAC, and as a target of bacterial virulence factors which hijack CD59 to lyse human cells.

immunology↗

bioRxiv2020

Structural basis for tuning activity and membrane specificity of bacterial cytolysins

Cholesterol-dependent cytolysins (CDCs) form protein nanopores to lyse cells. They target eukaryotic cells using different mechanisms, but all require the presence of cholesterol to pierce lipid bilayers. How CDCs use cholesterol to selectively lyse cells is essential for understanding virulence strategies of several pathogenic bacteria, and for repurposing CDCs to kill new cellular targets. Here we address that question by trapping an early state of pore formation for the CDC intermedilysin, bound to the human immune receptor CD59 in a nanodisc model membrane. Our cryo-electron microscopy map reveals structural transitions required for oligomerization, which include the lateral movement of a key amphipathic helix. We demonstrate that the charge of this helix is crucial for tuning lytic activity of CDCs. Furthermore, we discover modifications that overcome the requirement of cholesterol for membrane rupture, which will facilitate engineering the target-cell specificity of pore-forming proteins.

biochemistry↗