Effect of redox state on unfolding energetics of heme proteins

Both the enthalpic and entropic contributions to unfolding of three heme pr oteins, cytochrome b(562), cytochrome c and myoglobin, are larger for the r educed than for the oxidized form. Thus, the higher thermodynamic stability of a reduced, as compared to an oxidized, heme protein is the net result o f a large increase of favorable enthalpy and a small increase in unfavorabl e entropy. Upon comparing the unfolding energetics of the heme proteins to those of other single-domain proteins I find that protein length is the pri mary determinant of the thermodynamics. (C) 1999 Elsevier Science B.V. All rights reserved.