Biology subjects

Vickery, O. N.

Publications and source records attributed to Vickery, O. N..

5 recordsLinked to original sources

bioRxiv2021

CG2AT2: An Enhanced Fragment-based approach for Serial Multi-scale Molecular Dynamics simulations

Coarse-grained molecular dynamics provides a means for simulating the assembly and interactions of macromolecular complexes at a reduced level of representation, thereby allowing both longer timescale and larger sized simulations. Here, we describe an enhanced fragment-based protocol for converting macromolecular complexes from coarse-grained to atomistic resolution, for further refinement and analysis. While the focus is upon systems that comprise an integral membrane protein embedded in a phospholipid bilayer, the technique is also suitable for e.g. membrane-anchored and soluble protein/nucleotide complexes. Overall, this provides a method for generating an accurate and well equilibrated atomic-level description of a macromolecular complex. The approach is evaluated using a diverse test set of eleven system configurations of vary size and complexity. Simulations are assessed in terms of protein stereochemistry, conformational drift, lipid/protein interactions, and lipid dynamics.

biochemistry↗

bioRxiv2020

Ion-water coupling controls class A GPCR signal transduction pathways

G-protein-coupled receptors (GPCRs) transmit signals across the cell membrane, forming the largest family of membrane proteins in humans. Most GPCRs activate through an evolutionarily conserved mechanism, which involves reorientation of helices and key residues, rearrangement of a hydrogen bonding network mediated by water molecules, and the expulsion of a sodium ion from a protonatable binding site. However, how these components interplay to engage the signal effector binding site remains elusive. Here, we applied information theory to molecular dynamics simulations of pharmaceutically important GPCRs to trace concerted conformational variations across the receptors. We discovered a conserved communication pathway that includes protein residues and cofactors and enables the exchange of information between the extracellular sodium binding site and the intracellular G-protein binding region, coupling the most highly conserved protonatable residues at long distance. Reorientation of internal water molecules was found to be essential for signal transmission along this pathway. By inhibiting protonation, sodium decoupled this connectivity, identifying the ion as a master switch that determines the receptors ability to move towards active conformations.

biophysics↗

bioRxiv2019

Insights into Membrane Protein-Lipid Interactions from Free Energy Calculations

Integral membrane proteins are regulated by specific interactions with lipids from the surrounding bilayer. The structures of protein-lipid complexes can be determined through a combination of experimental and computational approaches, but the energetic basis of these interactions is difficult to resolve. Molecular dynamic simulations provide the primary computational technique to estimate the free energies of these interactions. We demonstrate that the energetics of protein-lipid interactions may be reliably and reproducibly calculated using three simulation-based approaches: potential of mean force calculations. alchemical free energy perturbation, and well-tempered metadynamics. We employ these techniques within the framework of a coarse-grained force field, and apply them to both bacterial and mammalian membrane protein-lipid systems. We demonstrate good agreement between the different techniques, providing a robust framework for their automated implementation within a pipeline for annotation of newly determined membrane protein structures.

biochemistry↗

bioRxiv2017

Modulation of the Neisseria gonorrhoeae drug efflux conduit MtrE

Widespread antibiotic resistance, especially of Gram-negative bacteria, has become a severe concern for human health. Tripartite efflux pumps are one of the major contributors to resistance in Gram-negative pathogens, by efficiently expelling a broad spectrum of antibiotics from the organism. In Neisseria gonorrhoeae, one of the first bacteria for which pan-resistance has been reported, the most expressed efflux complex is MtrCDE. Here we present the electrophysiological characterisation of the outer membrane component MtrE and the membrane fusion protein MtrC, obtained by a combination of planar lipid bilayer recordings and in silico techniques. Our in vitro results show that MtrE can be regulated by periplasmic binding events and that the interaction between MtrE and MtrC is sufficient to stabilize this complex in an open state. In contrast to other efflux conduits, the open complex only displays a slight preference for cations. The maximum conductance we obtain in the in vitro recordings is comparable to that seen in our computational electrophysiology simulations conducted on the MtrE crystal structure, indicating that this state may reflect a physiologically relevant open conformation of MtrE. Our results suggest that the MtrC/E binding interface is an important modulator of MtrE function, which could potentially be targeted by new efflux inhibitors.

biophysics↗

bioRxiv2017

Intracellular Passage Of Na+ In An Active State G Protein Coupled Receptor

Playing a central role in cell signalling, GPCRs have evolved into the largest superfamily of membrane proteins and form the majority of drug targets in humans. How extracellular agonist binding triggers the activation of GPCRs and associated intracellular effector proteins remains, however, poorly understood. High resolution structural studies have recently revealed that inactive class-A GPCRs harbour a conserved binding site for Na+ ions in the centre of their transmembrane domain, accessible from the extracellular space. Here, we show that the opening of a conserved hydrated channel in the activated state receptors allows the Na+ ion to egress from its binding site into the cytosol. Coupled with protonation changes, this ion movement occurs without significant energy barriers, and can be driven by physiological transmembrane ion and voltage gradients. We propose that Na+ ion exchange with the cytosol is a key step in GPCR activation, which locks receptors in long-lived active-state conformations.

biophysics↗