Jost Lopez A, Quoika PK, Linke M, Hummer G, Köfinger J. Quantifying Protein-Protein Interactions in Molecular Simulations.
J Phys Chem B 2020;
124:4673-4685. [PMID:
32379446 PMCID:
PMC7294537 DOI:
10.1021/acs.jpcb.9b11802]
[Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
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Interactions
among proteins, nucleic acids, and other macromolecules
are essential for their biological functions and shape the physicochemcial
properties of the crowded environments inside living cells. Binding
interactions are commonly quantified by dissociation constants Kd, and both binding and nonbinding interactions
are quantified by second osmotic virial coefficients B2. As a measure of nonspecific binding and stickiness, B2 is receiving renewed attention in the context
of so-called liquid–liquid phase separation in protein and
nucleic acid solutions. We show that Kd is fully determined by B2 and the fraction
of the dimer observed in molecular simulations of two proteins in
a box. We derive two methods to calculate B2. From molecular dynamics or Monte Carlo simulations using implicit
solvents, we can determine B2 from insertion
and removal energies by applying Bennett’s acceptance ratio
(BAR) method or the (binless) weighted histogram analysis method (WHAM).
From simulations using implicit or explicit solvents, one can estimate B2 from the probability that the two molecules
are within a volume large enough to cover their range of interactions.
We validate these methods for coarse-grained Monte Carlo simulations
of three weakly binding proteins. Our estimates for Kd and B2 allow us to separate
out the contributions of nonbinding interactions to B2. Comparison of calculated and measured values of Kd and B2 can be
used to (re-)parameterize and improve molecular force fields by calibrating
specific affinities, overall stickiness, and nonbinding interactions.
The accuracy and efficiency of Kd and B2 calculations make them well suited for high-throughput
studies of large interactomes.
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