Premium
Coupling between conformation and proton binding in proteins
Author(s) -
Vila Jorge A.,
Ripoll Daniel R.,
Arnautova Yelena A.,
Vorobjev Yury N.,
Scheraga Harold A.
Publication year - 2005
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.20531
Subject(s) - ionization , chemistry , solvation , charge density , chemical physics , poisson distribution , charge (physics) , electrostatics , molecule , native state , implicit solvation , computational chemistry , proton , partial charge , physics , crystallography , ion , quantum mechanics , mathematics , statistics , organic chemistry
Abstract Interest centers here on whether the use of a fixed charge distribution of a protein solute, or a treatment that considers proton‐binding equilibria by solving the Poisson equation, is a better approach to discriminate native from non‐native conformations of proteins. In this analysis of the charge distribution of 7 proteins, we estimate the solvation free energy contribution to the total free energy by exploring the 2 ζ possible ionization states of the whole molecule, with ζ being the number of ionizable groups in the amino acid sequence, for every conformation in the ensembles of 7 proteins. As an additional consideration of the role of electrostatic interactions in determining the charge distribution of native folds, we carried out a comparison of alternative charge assignment models for the ionizable residues in a set of 21 native‐like proteins. The results of this work indicate that (1) for 6 out of 7 proteins, estimation of solvent polarization based on the Generalized Born model with a fixed charge distribution provides the optimal trade‐off between accuracy, with respect to the Poisson equation, and speed when compared to the accessible surface area model; for the seventh protein, consideration of all possible ionization states of the whole molecule appears to be crucial to discriminate the native from non‐native conformations; (2) significant differences in the degree of ionization and hence the charge distribution for native folds are found between the different charge models examined; (3) the stability of the native state is determined by a delicate balance of all the energy components, and (4) conformational entropy, and hence the dynamics of folding, may play a crucial role for a successful ab initio protein folding prediction. Proteins 2005. © 2005 Wiley‐Liss, Inc.