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Analysis of side chain mobility among protein G B1 domain mutants with widely varying stabilities
Author(s) -
Goehlert Virginia A.,
Krupinska Ewa,
Regan Lynne,
Stone Martin J.
Publication year - 2004
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.04926604
Subject(s) - conformational entropy , side chain , chemistry , mutant , molecular dynamics , entropy (arrow of time) , configuration entropy , protein folding , thermodynamics , crystallography , computational chemistry , physics , biochemistry , molecule , organic chemistry , gene , polymer
Abstract “Host–guest” studies of the B1 domain from Streptococcal protein G have been used previously to establish a thermodynamic scale for the β‐sheet‐forming propensities of the 20 common amino acids. To investigate the contribution of side chain conformational entropy to the relative stabilities of B1 domain mutants, we have determined the dynamics of side chain methyl groups in 10 of the 20 mutants used in a previous study. Deuterium relaxation rates were measured using two‐dimensional NMR techniques for 13 CH 2 D groups. Analysis of the relaxation data using the Lipari–Szabo model‐free formalism showed that mutations introduced at the guest position caused small but statistically significant changes in the methyl group dynamics. In addition, there was a low level of covariation of the Lipari–Szabo order parameters among the 10 mutants. The variations in conformational free energy estimated from the order parameters were comparable in magnitude to the variations in global stability of the 10 mutants but did not correlate with the global stability of the domain or with the structural properties of the guest amino acids. The data support the view that conformational entropy in the folded state is one of many factors that can influence the folding thermodynamics of proteins.