Complex Formation with the Activator RACo Affects the Corrinoid Structure of CoFeSP

Abstract

Activation of the corrinoid [Fe-S] protein (CoFeSP), involved in reductive CO₂ conversion, requires the reduction of the Co­(II) center by the [Fe-S] protein RACo, which according to the reduction potentials of the two proteins would correspond to an uphill electron transfer. In our resonance Raman spectroscopic work, we demonstrate that, as a conformational gate for the corrinoid reduction, complex formation of Co­(II)­FeSP and RACo specifically alters the structure of the corrinoid cofactor by modifying the interactions of the Co­(II) center with the axial ligand. On the basis of various deletion mutants, the potential interaction domains on the partner proteins can be predicted