Biology subjects

Gurvic, D.

Publications and source records attributed to Gurvic, D..

3 recordsLinked to original sources

bioRxiv2025

Structural Basis of Lipopolysaccharide Assembly by the Outer Membrane Translocon Holo-Complex

Lipopolysaccharide (LPS) assembly at the surfaces-exposed leaflet of the bacterial outer membrane (OM) is mediated by the OM LPS translocon. An essential transmembrane {beta}-barrel protein, LptD, and a cognate lipoprotein, LptE, translocate LPS selectively into the OM external leaflet via a poorly understood mechanism. Here, we characterize two additional translocon subunits, the lipoproteins LptM and LptY (formerly YedD). We use single-particle cryo-EM analysis, functional assays and molecular dynamics simulations to visualize the roles of LptM and LptY at the translocon holo-complex LptDEMY, uncovering their impact on LptD conformational dynamics. Whereas LptY binds and stabilizes the periplasmic LptD {beta}-taco domain that functions as LPS receptor, LptM intercalates the lateral gate of the {beta}-barrel domain, promoting its opening and access by LPS. Remarkably, we demonstrate a conformational switch of the LptD {beta}-taco/{beta}-barrel interface alternating between contracted and extended states. The LptD {beta}-strand 1, which defines the mobile side of the lateral gate, binds LPS and performs a stroke movement toward the external leaflet during the contracted-to-extended state transition. Our findings establish a detailed mechanistic framework explaining the selective transport of LPS to the membrane external leaflet.

microbiology↗

bioRxiv2023

Multidrug Efflux in Gram-Negative Bacteria: Rationally Modifying Compounds to Avoid Efflux Pumps

Gram-negative bacteria cause the majority of critically drug-resistant infections, necessitating the rapid development of new drugs with Gram-negative activity. However, drug design is hampered by the low permeability of the Gram-negative cell envelope and the function of drug efflux pumps, which extrude foreign molecules from the cell. A better understanding of the molecular determinants of compound recognition by efflux pumps is, therefore, essential. Here, we quantitatively analyse the activity of over 73,000 compounds across three strains of E. coli - the wild-type, an efflux-deficient variant, and a hyper-permeable variant - to elucidate the molecular principles of evading efflux pumps. Our results show that, alongside a range of physicochemical features, the presence or absence of specific chemical groups in the compounds substantially increases the probability of avoiding efflux. Furthermore, comparison of our findings with inward permeability data highlights the primary role of efflux in determining drug bioactivity in Gram-negative bacteria.

pharmacology and toxicology↗

bioRxiv2020

Positively selected modifications in the pore of TbAQP2 allow pentamidine to enter Trypanosoma brucei

Mutations in the Trypanosoma brucei aquaporin AQP2 are associated with resistance to pentamidine and melarsoprol. We show that TbAQP2 but not TbAQP3 was positively selected for increased pore size from a common ancestor aquaporin. We demonstrate that TbAQP2s unique architecture permits pentamidine permeation through its central pore and show how specific mutations in highly conserved motifs affect drug permeation. Introduction of key TbAQP2 amino acids into TbAQP3 renders the latter permeable to pentamidine. Molecular dynamics demonstrates that permeation by dicationic pentamidine is energetically favourable in TbAQP2, driven by the membrane potential, although aquaporins are normally strictly impermeable for ionic species. We also identify the structural determinants that make pentamidine a permeant but exclude most other diamidine drugs. Our results have wide-ranging implications for optimising antitrypanosomal drugs and averting cross-resistance. Moreover, these new insights in aquaporin permeation may allow the pharmacological exploitation of other members of this ubiquitous gene family.

biochemistry↗