CONFORMATIONAL DEPENDENCE OF CARBON-MONOXIDE LIGATION DYNAMICS IN CYTOCHROME-C-OXIDASE

Time-resolved optical studies have recently demonstrated that ligand photolysis and rebinding in fully reduced cytochrome c oxidase (Cco) is an extremely complicated process involving structural dynamics of both the proximal and distal heme pockets of cytochrome a3. We have expanded upon these studies by examining the corresponding ligation dynamics in mixed-valence (MV) Cco, which is known to exist in a conformation that is structurally and kinetically distinct from fully reduced (FR) Cco. We report here time-resolved Raman results showing that while the promximal heme pocket dynamics of MV-Cco are similar to those of FR-Cco, the ligation dynamics of the distal pocket are affected by the protein conformational state.