Picosecond infrared study of the photodynamics of carbonmonoxy-cytochrome c oxidase.

Time-resolved infrared (TRIR) techniques have been employed to study the reactions of carbon monoxide with the cytochrome alpha 3-Cu(B) site of cytochrome c oxidase (CcO). The ligation dynamics immediately following photodissociation have been investigated using picosecond TRIR spectroscopy and linear dichroism. The rate of photoinitiated transfer of CO from cytochrome alpha 3 to CuB was measured directly by monitoring the development of the transient CuBCO absorption. In less than 1 ps, a stationary CuBCO spectrum develops, which together with the CO infrared linear dichroism is constant until the CO dissociates from CuB on a microsecond time scale. These observations indicate that the CO is transferred between metals and reaches its equilibrium conformation in less than 1 ps. This unprecedented ligand transfer rate has profound implications with regard to the structure and dynamics of the cytochrome alpha 3-CuB site, the functional architecture of the protein, and coordination dynamics in general.