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Structural and functional characteristics of polypeptide subunits of the bovine heart ubiquinol—cytochrome‐ c reductase complex

1991; Wiley; Volume: 195; Issue: 3 Linguagem: Inglês

10.1111/j.1432-1033.1991.tb15760.x

1432-1033

Tiziana Cocco, Michele Lorusso, Anna Maria Sardanelli, Michele Minuto, Severino Ronchi, Gabriella Tedeschi, Sergio Papa,

Mass Spectrometry Techniques and Applications

Structural and functional characteristics of subunits of bovine heart cytochrome-c reductase have been investigated by controlled digestion of soluble and membrane-reconstituted purified bc1 complex and direct amino acid sequencing of native and digested protein subunits. The results obtained show that the N-terminal segments of core protein II and the 14-kDa protein extend at the periphery of the complex, protruding into the inner matrix space. The Fe-S protein, located at the outer C-periphery of the complex, is shown to be anchored to other subunits of the complex by the amphipathic N-terminal region. Proteolytic cleavage of 7-11 residues from the N-terminal segment of the 14-kDa protein is apparently associated with decoupling of redox-linked proton pumping. Partial digestion of core protein II, the 6.4-kDa protein, and the C-terminal region of the 9.2-kDa protein, is without effect on the redox and proton-motive activity of the complex.