Pro → Ala-35Rhodobacter capsulatuscytochromec2shows dynamic not structural differences

Abstract

Comparative analysis of nuclear Overhauser effects show that the time average conformation of the wild-type and mutant Pro → Ala-35 Rhodobacter capsulatus cytochrome c2 are indistinguishable. The ring resonances of Phe-51 and Tyr-53 show that their ring flip rates increase in P35A. NH proton exchange studies show that the exchange rates of the NH of Gly-34 and the NπH of His-17 increase by ≈ 102 in P35A suggesting that their respective hydrogen bonds are destabilized in this protein. However, 3αNH.1H and 15N chemical shift data argue that these bonds are intact. These data are compatible if the replacement of a Pro with an Ala residue forms a cavity or increases local flexibility thus reducing steric hinderance and increasing solvent accessibility