Isolation and amino acid sequence of a novel 6.8-kDa mitochondrial proteolipid from beef heart. Use of FAB-MS for molecular mass determination.

We have isolated a 6.8 kDa proteolipid from an acidic chloroform/methanol extract of bovine cardiac muscle. The molecular mass of the polypeptide was measured by fast atom bombardment-mass spectrometry (FAB-MS) (m/z6834.1). Its amino acid sequence was partly determined by direct sequencing and completed by characterization of cyanogen bromide and tryptic fragments (sequencing, FAB-MS and amino acid analysis). The polypeptide consists of 60 amino acid residues. Polyclonal antibodies raised in rabbit allowed its localization by electroimmunoblotting in mitochondria.