Mutations Pro → Ala-35 and Tyr → Phe-75 of Rhodobacter capsulatus Ferrocytochrome c2Affect Protein Backbone Dynamics: Measurements of Individual Amide Proton Exchange Rate Constants by 1H-15N HMQC Spectroscopy

Abstract

Comparisons of hydrogen-deuterium solvent exchange rate constants for the NH protons of wild-type Pro → Ala-35 (P35A) and Tyr → Phe-75 (Y75F) Rhodobacter capsulatus ferrocytochromes c2were made by 1H-15N heteronuclear multiple-quantum correlation spectroscopy. Exchange rate constants increased for the NH protons of residues 45-46, 54, 57-58, 60-61, 82-87, 98, and 100 with Y75F and 16-18, 20, 34, 37, 43, 45-46, and 58 with P35A. The increases in exchange rate constants are consistent with changes in unfolding equilibria and protein dynamics. In Y75F the exchange rate constants of the observable NH protons of the helix spanning Pro-79-Asp-89, namely Phe-82-Leu-87, increase to a similar degree,..