Allosteric regulation based on the heme redox state has been implicated in a variety of biological systems but the mechanistic principles of these rearrangements remain unclear. We examine redox-linked H2O-to-Met ligand substitution in a Geobacter sulfurreducens heme sensor GSU0935 and further rationalize factors governing this and other types of heme ligand switching with model cytochrome c variants. Comparison of folding thermodynamics for ferric and ferrous GSU0935 suggests the relatively small difference in the stability of the two redox states. Refolding of GSU0935 proceeds through a low-spin heme intermediate. The multiple ligation states and their interconversion during folding and redox reactions illustrate the great flexibility of the heme environment in this sensor protein. Ligand substitution alters the redox reactivity of the heme group in proteins and we systematically analyze such changes in photoinduced electron transfer studies of Met80X mutants of cytochrome c.

Redox-linked conformational rearrangements in heme proteins

243rd National Meeting (2012)

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