Interactions of a Polypeptide with a Protein Nanopore Under Crowding Conditions
- 29 March 2019
- journal article
- research article
- Published by American Chemical Society (ACS) in ACS Nano
- Vol. 13 (4), 4469-4477
- https://doi.org/10.1021/acsnano.9b00008
Abstract
Molecular crowding, a ubiquitous feature of the cellular environment, has significant implications in the kinetics and equilibrium of biopolymer interactions. In this study, a single charged polypeptide is exposed to competing forces that drive it into a transmembrane protein pore versus forces that pull it outside. Using single-molecule electrophysiology, we provide compelling experimental evidence that the kinetic details of the polypeptide–pore interactions are substantially affected by high concentrations of less-penetrating polyethylene glycols (PEGs). At a polymer concentration above a critical value, the presence of these neutral macromolecular crowders increases the rate constant of association but decreases the rate constant of dissociation, resulting in a stronger polypeptide–pore interaction. Moreover, a larger-molecular weight PEG exhibits a lower rate constant of association but a higher rate constant of dissociation than those values corresponding to a smaller-molecular weight PEG. These outcomes are in accord with a lower diffusion constant of the polypeptide and higher depletion–attraction forces between the polypeptide and transmembrane protein pore under crowding and confinement conditions.Keywords
Funding Information
- National Institute of General Medical Sciences (GM129429, GM088403)
- Division of Materials Research (DMR-1460784)
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