Isolation and structural characterization of porcine coupling factor 6 from intestinal tissues.

A polypeptide purified from an extract of thermostable, porcine intestinal peptides was found to correspond to coupling factor 6, previously known as a component of the mitochondrial oxidative phosphorylation system. The intestinal presence of this peptide offers a new source for preparation of the component in large quantities, and possibly suggests further functions of the polypeptide. Amino acid sequence analysis of this porcine form reveals it to be identical to the bovine form, except for two replacements, at position 62 (Thr in the porcine, Phe/Thr in the bovine form), and position 70 (Ala/Val). The extensive conservation suggests strict structural constraints on the functional properties of the polypeptide.