Circularization changes the folding transition state of the src SH3 domain

TitleCircularization changes the folding transition state of the src SH3 domain
Publication TypeJournal Article
Year of Publication2001
AuthorsGrantcharova, V. P., & Baker D.
JournalJournal of molecular biology
Volume306
Issue3
Pagination555-63
Date Published2001 Feb 23
ISSN0022-2836
KeywordsAmino Acid Substitution, Disulfides, Entropy, Kinetics, Point Mutation, Primary Publication, Protein Folding, src Homology Domains, src-Family Kinases
Abstract

Native state topology has been implicated as a major determinant of protein-folding mechanisms. Here, we test experimentally the robustness of the src SH3-domain folding transition state to changes in topology by covalently constraining regions of the protein with disulfide crosslinks and then performing kinetic analysis on point mutations in the context of these modified proteins. Circularization (crosslinking the N and C termini) of the src SH3 domain makes the protein topologically symmetric and causes delocalization of structure in the transition state ensemble suggesting a change in the folding mechanism. In contrast, crosslinking a single structural element (the distal beta-hairpin) which is an essential part of the transition state, results in a protein that folds 30 times faster, but does not change the distribution of structure in the transition state. As the transition states of distantly related SH3 domains were previously found to be very similar, we conclude that the free energy landscape of this protein family contains deep features which are relatively insensitive to sequence variations but can be altered by changes in topology.

Alternate JournalJ. Mol. Biol.
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