Folding kinetics of the SH3 domain of PI3 kinase by real-time NMR combined with optical spectroscopy

Abstract

The refolding kinetics of the chemically denatured SH3 domain of phosphatidylinositol 3'-kinase (PI3-SH3) have been monitored by real-time one-dimensional 1H NMR coupled with a variety of other biophysical techniques. These experiments indicate that the refolding kinetics of PI3-SH3 are biphasic. The slow phase (27 (± 8)% amplitude) is due to a population of substantially unfolded molecules with an incorrectly configured cis proline residue. The fast phase (73 (± 8)% amplitude) corresponds to the folding of protein molecules with proline residues in a trans configuration in the unfolded state. NMR experiments indicate that the first species populated after the initiation of folding exhibit p..