Ashkinadze, D. | Search bioRxiv

bioRxiv2021

Atomic resolution Protein Allostery from the multi-state Structure of a PDZ Domain

Recent methodological advances in solution NMR allow the determination of multi-state protein structures and provide insights into correlated motion at atomic resolution as demonstrated here for the well-studied PDZ2 domain of protein human tyrosine phosphatase 1E for which protein allostery was predicted. Two-state protein structures were calculated for both the free form and in complex with the RA-GEF2 peptide using the exact nuclear Overhauser effect (eNOE) method. In the apo protein states an allosteric conformational preselection step comprising almost 60% of the domain was detected with an "open" ligand welcoming state and a "closed" state that obstructs the binding site by the distance between the {beta}-sheet, -helix 2 and sidechains of residues Lys38 and Lys72. Observed apo-holo structural rearrangements of induced fit-type are in line with previously published evolution-based analysis covering ~25% of the domain with only a partial overlap with the protein allostery of the open form. These presented structural studies highlight the presence of a dedicated highly optimized dynamic interplay of the complexity of the PDZ2 domain owed by the structure-dynamics landscape.

biophysics↗

bioRxiv2020

Mass Photometry of Membrane Proteins

Integral membrane proteins (IMPs) are biologically highly significant but challenging to study because they require maintaining a cellular lipid-like environment. Here, we explore the application of mass photometry (MP) to IMPs and membrane mimetic systems at the single particle level. We apply MP to amphipathic vehicles, such as detergents and amphipols, as well as to lipid and native nanodiscs, characterising the particle size, sample purity and heterogeneity. Using methods established for cryogenic electron microscopy, we eliminate detergent background, enabling high-resolution studies of membrane protein structure and interactions. We find evidence that, when extracted from native membranes using native styrene-maleic acid nanodiscs, the potassium channel KcsA is present as a dimer of tetramers - in contrast to results obtained using detergent purification. Finally, using lipid nanodiscs, we show that MP can help distinguish between functional and non-functional nanodisc assemblies, as well as determine the critical factors for lipid nanodisc formation.

biophysics↗