Purification and spectral characterization of a b-type cytochrome from the plasma membrane of the archaebacterium Sulfolobus acidocaldarius

For the first time the purification of a heme-b containing cytochrome from the plasma membrane of an extremely thermoacidophilic archaebacterium is described. The detergent solubilized 30 kDa polypeptide contains two heme-b centers and one copper ion. According to its low temperature spectra and CO-binding properties, it is likely to function as a cytochrome-o like terminal oxidase in the membrane. The purified cytochrome does not retain catalytic activity, however.