Circularization changes the folding transition state of the src SH3 domain11Edited by C. R. Matthews

Viara P Grantcharova, David Baker
2001 Journal of Molecular Biology  
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 disul®de crosslinks and then performing kinetic analysis on point mutations in the context of these modi®ed proteins. Circularization (crosslinking the N and C termini) of the src SH3 domain makes the protein topologically symmetric
more » ... d 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 b-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.
doi:10.1006/jmbi.2000.4352 pmid:11178913 fatcat:byna7d75ifgm3pg2kl57ge65um