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The origins of asymmetry in the folding transition states of protein L and protein G
Author(s) -
Karanicolas John,
Brooks Charles L.
Publication year - 2002
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.0205402
Subject(s) - protein folding , topology (electrical circuits) , contact order , folding (dsp implementation) , entropy (arrow of time) , physics , crystallography , biophysics , chemistry , biology , microbiology and biotechnology , combinatorics , thermodynamics , mathematics , engineering , electrical engineering
Topology has been shown to be an important determinant of many features of protein folding; however, the delineation of sequence effects on folding remains obscure. Furthermore, differentiation between the two influences proves difficult due to their intimate relationship. To investigate the effect of sequence in the absence of significant topological differences, we examined the folding mechanisms of segment B1 peptostreptococcal protein L and segment B1 of streptococcal protein G. These proteins share the same highly symmetrical topology. Despite this symmetry, neither protein folds through a symmetrical transition state. We analyzed the origins of this difference using theoretical models. We found that the strength of the interactions present in the N‐terminal hairpin of protein L causes this hairpin to form ahead of the C‐terminal hairpin. The difference in chain entropy associated with the formation of the hairpins of protein G proves sufficient to beget initiation of folding at the shorter C‐terminal hairpin. Our findings suggest that the mechanism of folding may be understood by examination of the free energy associated with the formation of partially folded microstates.