Folding dynamics of the src SH3 domain

Area of Science:

• Protein folding and biophysics
• Molecular dynamics and protein structure

Background:

• SH3 domains are crucial protein modules involved in signal transduction.
• Understanding protein folding mechanisms is key to deciphering protein function and dysfunction.

Purpose of the Study:

• To characterize the thermodynamics and kinetics of chicken src SH3 domain folding.
• To investigate the cooperative nature of unfolding and the structure of the denatured state.

Main Methods:

• Equilibrium and stopped-flow fluorescence spectroscopy
• Circular dichroism (CD) spectroscopy
• Nuclear magnetic resonance (NMR) hydrogen-deuterium exchange experiments

Main Results:

• Chicken src SH3 domain folding follows a two-state mechanism, confirmed by fluorescence, CD, and kinetic studies.
• Thermodynamic parameters (entropy, enthalpy, heat capacity) were determined.
• Hydrogen-deuterium exchange revealed a cooperative unfolding process with a compact denatured state.

Conclusions:

• The src SH3 domain exhibits cooperative folding and unfolding.
• The denatured state may retain some compactness under native conditions.
• Insights into folding determinants and protein stability were gained through comparison with homologous domains.