Properties of a copper-containing cytochrome c1aa3 complex: a terminal oxidase of the extreme thermophile Thermus thermophilus HB8.

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Abstract
From the plasma membrane of T. thermophilus HB8 a detergent-solubilized complex of cytochromes a and c1 that actively catalyzes the transfer of electrons from ascorbate via a redox dye to O2 was partially purified. The complex is composed of 2 types of polypeptides, with MW of .apprxeq. 55,000 and 33,000. Quantitative analyses revealed the presence of heme a, heme c, and Cu in a ratio of 2:1:2, with heme a present at 10 .+-. 1.3 nmol/mg of protein. The heme c was associated with the MW 33,000 peptide and may be of the c1 type. The optical and EPR properties of this complex were similar to those of eukaryotic cytochrome oxidase, suggesting the following arrangement of chromophores: a magnetically isolated cytochrome c1 and an O2-reducing functional unit consisting of 2 heme a groups and 2 Cu ions associated with 1 or more larger peptides.