Hydrogenophilus thermoluteoluscytochromec¢ (PHCP) has typical spectral properties previously observed for other cytochromesc¢, which comprise Ambler’s class II cytochromesc. The PHCP protein sequence (135 amino acids) deduced from the cloned gene is the most homologous (55% iden-tity) to that of cytochrome c¢ from Allochromatium vinosum(AVCP).