We have designed de novo 13 divergent spectrin SH3 core sequences to determine their folding properties. Kinetic analysis of the variants with stability similar to that of the wild type protein shows accelerated unfolding and refolding rates compatible with a preferential stabilization of the transition state. This is most likely caused by conformational strain in the native state, as deletion of a methyl group (Ile-->Val) leads to deceleration in unfolding and increased stability (up to 2 kcal x mol(-1)). Several of these Ile-->Val mutants have negative phi(-U) values, indicating that some noncanonical phi(-U) values might result from conformational strain. Thus, producing a stable protein does not necessarily mean that the design process has been entirely successful. Strained interactions could have been introduced, and a reduction in the buried volume could result in a large increase in stability and a reduction in unfolding rates. Study holds ProTherm entries: 15221, 15222, 15223, 15224, 15225, 15226, 15227, 15228, 15229, 15230, 15231, 15232, 15233, 15234, 15235, 15236, 15237, 15238, 15239 Extra Details: kinetic analysis; transition state; methyl group; strained interactions
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:46 p.m.
|Number of data points||56|
|Proteins||Spectrin alpha chain, non-erythrocytic 1 ; Spectrin alpha chain, non-erythrocytic 1|
|Assays/Quantities/Protocols||Experimental Assay: m ; Experimental Assay: dG_H2O ; Derived Quantity: ddG_H2O|
|Libraries||Mutations for sequence MDETGKELVLALYDYQEKSPREVTMKKGDILTLLNSTNKDWWKVEVNDRQGFVPAAYVKKLD|