J. Biol. Chem., Vol. 261, Issue 20, 9206-9209, 07, 1986
The nuclear-coded subunits of yeast cytochrome c oxidase. The amino acid sequences of subunits VII and VIIa, structural similarities between the three smallest polypeptides of the holoenzyme, and implications for biogenesis
SD Power, MA Lochrie and RO Poyton
The complete amino acid sequences of subunits VII and VIIa from yeast
cytochrome c oxidase are reported. Subunits VII and VIIa are 57 residues
(Mr = 6603) and 54 residues (Mr = 6303) in length, respectively. Both
polypeptides are amphiphilic, have an internal hydrophobic section and
hydrophilic NH2 and COOH termini, and terminate at their COOH termini with
a basic amino acid. This structural motif is similar to that possessed by
subunit VIII of yeast cytochrome c oxidase. All three polypeptides have
hydrophobic sections which are long enough to span the inner membrane; all
three polypeptides lack methionine at their NH2 termini; and all three
polypeptides have COOH termini which could result from proteolysis by a
protease with trypsin or cathepsin B-like activity. These observations
raise the interesting possibility that subunits VII, VIIa, and VIII are
transmembranous polypeptides which are processed at both their NH2 and COOH
termini during their biogenesis.
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