Isolation and amino acid sequence of the 'Rieske' iron sulfur protein of beef heart ubiquinol:cytochrome c reductase

Abstract

The sequence of the 'Rieske' iron sulfur protein from the bc1 complex of beef heart mitochondria has been determined by solid phase Edman degradation of the whole protein and of various proteolytic fragments. The protein consists of 196 amino acid residues. The molecular mass of the apoprotein was calculated to be 21,536 Da, that of the holo-protein including the Fe2S2 cluster as 21,708 Da. The protein is mainly hydrophilic with a polarity index of 42.9% and 25% of charged residues. It contains a hydrophobic membrane anchor which is predicted to form a 'hairpin' structure. The iron sulfur cluster is bound near the C-terminus of the protein between a hydrophobic and a more amphipathic domain. This reflects the fact that the cluster is located near the outer surface of the inner mitochondrial membrane. A folding pattern describing all known features of the protein is proposed.