CYTOCHROME C1 COMPLEXES

  • 1 January 1979
    • journal article
    • research article
    • Vol. 254  (6) , 1845-1853
Abstract
Bovine heart cytochrome c1 forms an active complex with cytochrome c as previously reported. It also forms a complex with cytochrome oxidase with heme ratio of 1:1. This cytochrome c1.cntdot.oxidase complex was purified by ammonium sulfate fractionation and is stable in media of high ionic strength (> 0.1 M) but dissociates as the pH deviates from neutral. The purified cytochrome c1 aggregates to an oligomer, presumably a pentamer. No agent has been found to depolymerize isolated c1 without denaturation. In the cytochrome c1.cntdot.oxidase complex, these 2 cytochromes apparently were depolymerized to form smaller aggregates, if not monomeric units, as judged by sedimentation behavior. Cytochrome c1 also forms a ternary complex with cytochrome c and oxidase in the heme ratio of 1:1:1. This complex can be prepared by any of the following 4 methods: c1 + c + oxidase; c1.cntdot.c complex + oxidase, c1 + c.cntdot.oxidase complex; or c + c1.cntdot.oxidase complex. The mode of formation of these complexes is all from pure protein-protein interactions. Cytochrome c1 is also incorporated into phospholipid vesicles and these vesicles show about 200 molecules of phospholipid/cytochrome C1 in terms of heme. The spectrophotometric, circular dichroic, sedimentation behavior and enzymatic properties of these complexes were investigated.