Abstact

It has been demonstrated that the complex of yeast cytochrome c (Cc) and cytochrome c peroxidase (CcP) exists as a delicate equilibrium of a specific, active state and the non-specific, dynamic encounter state. An ortholog of yeast Cc, horse Cc, binds CcP but forms a much more dynamic complex, as demonstrated by NMR spectroscopy. A single conservative mutation of lysine 13 to arginine reduces the dynamics and enhances the specificity. The crystal structure of the stereospecific complex resembles the yeast Cc-CcP complex. In contrast, the K13A mutation increases the dynamic nature of the complex with CcP, showing that specificity in a redox protein complex can depend on the interactions of a single side chain in the binding interface.