Two membrane-bound c-type cytochromes of Thiobacillus ferrooxidans: purification and properties.

Membrane-bound cytochrome c, cytochrome c-552 (m) was purified from Thiobacillus ferrooxidans. It showed an absorption peak at 410 nm in the oxidized form, and peaks at 552, 523 and 416 nm in the reduced form. Its molecular mass, Em,7 and isoelectric point were 22,300, +0.336 volt and 9.1, respectively. Another membrane-bound cytochrome c, cytochrome c-550 (m) was also purified. It showed an absorption peak at 408 nm in the oxidized form, and peaks at 550, 523 and 418 nm in the reduced form. Its molecular mass was estimated to be 51,000. Ferrocytochromes c-552 (m) and c-550 (m) were oxidized by cytochrome c oxidase of the bacterium. The reactivity with the oxidase of cytochrome c-550 (m) was higher than that of cytochrome c-552 (s) (soluble cytochrome) of the bacterium, while the reactivity of cytochrome c-552 (m) was greatly lower than that of cytochrome c-552 (s).