The structure of an electron transfer complex containing a cytochrome c and a peroxidase

Efficient biological electron transfer may require a fluid association of r edox partners. Two noncrystallographic methods (a new molecular docking pro gram and H-1 NMR spectroscopy) have been used to study the electron transfe r complex formed between the cytochrome c peroxidase (CCP) of Paracoccus de nitrificans and cytochromes c, For the natural redox partner, cytochrome c( 550), the results are consistent with a complex in which the heme of a sing le cytochrome lies above the exposed electron-transferring heme of the pero xidase. In contrast, two molecules of the nonphysiological but kinetically competent horse cytochrome bind between the two hemes of the peroxidase. Th ese dramatically different patterns are consistent with a redox active surf ace on the peroxidase that may accommodate more than one cytochrome and all ow lateral mobility.