N-terminal amino acid sequence of the Rieske iron-sulfur protein from the cytochrome b6/f-complex of spinach thylakoids

AbstractThe 20 kDa subunit of the cytochrome b6/f-complex, the Rieske iron-sulfur protein, was isolated by preparative SDS-PAGE. For automatic Edman degradation the protein was recovered by electrophoretic elution. Several peptides were purified after tryptic, CNBr or Arg C endopeptidase digestion or cleavage at Trp-residues. The determination of the amino acid sequence of these peptides yielded overlapping sequences for a total of 96 amino acids starting at the N-terminus. This sequence shows no homology to the primary structure of the two Rieske FeS proteins already published by other authors. But like these it contains a hydrophobic sequence of 30 amino acids close to the N-terminal indicating the sequence that spans the membrane. Two polypeptides, closer to the C-terminus, contained sequences which are also present in Neurospora crassa and Rhodopseudomonas sphaeroides including a Cys-Pro-Cys containing sequence involved in iron binding