Role of cytochrome b562 in the archaeal aerobic respiratory chain of Sulfolobus sp. strain 7.

The role of cytochrome b562, a fragile constituent of the respiratory terminal oxidase supercomplex of the thermoacidophilic archaeon, Sulfolobus sp. strain 7, was investigated spectroscopically in the membrane-bound state. Cytochrome b562 did not react with CO or cyanide in the membrane-bound state, while it was irreversibly modified to a CO-reactive form (b59) upon solubilization in the presence of cholate and LiCl. Cyanide titration analyses with the succinate-reduced membrane suggested that cytochrome b562 was upstream of both the "gy = 1.89' Rieske FeS cluster and the a-type cytochromes. These results show that the b-type cytochrome functions as an intermediate electron transmitter in the terminal oxidase supercomplex.