Purification and some properties of cytochrome c-552 from an extreme thermophile, Thermus thermophilus HB8.

A c-type cytochrome, cytochrome c-552, from a soluble fraction of an extreme thermophile, Thermus thermophilus HB8, was highly purified and its properties investigated. The absorption peaks were at 552, 522, and 417 nm in the reduced form, and at 408 nm in the oxidized form. The isoelectric point was at PH 10.8, the midpoint redox potential was about +0.23 V, and the molecular weight was about 15,000. The cytochrome c-552 was highly thermoresistant. The cytochrome reacted rapidly with pseudomonas aeruginosa nitrite reductase [EC 1.9.3.2], but slowly with bovine cytochrome oxidase [EC 1.9.3.1], yeast cytochrome c peroxidase [EC 1.11.1.5], or Nitrosomonas europaea hydroxylamine-cytochrome c reductase [EC 1.7.3.4].