Characterization of the Rat Apolipoproteins

Abstract

The apolipoproteins from rat plasma high density lipoproteins were separated into three fractions by Sephadex gel chromatography. Five low molecular weight proteins were purified from the last Sephadex fraction by ion exchange chromatography. All five proteins have apparent homologues among the human apolipoproteins. The A-II apoprotein has COOH-terminal alanine, a blocked NH2 terminus and contains no histidine, tryptophan or cysteine. Unlike human A-II, it appears to occur in monomeric form. The C-I apoprotein has COOH-terminal alanine, NH2-terminal aspartic acid, contains 16% lysine, and lacks valine, tyrosine, and cysteine. The C-II apoprotein has NH2-terminal threonine, COOH-terminal glutamic acid and contains no cysteine. Two forms of the C-III apoprotein were found with COOH-terminal proline and NH2-terminal aspartic acid. One form, C-III-0, contains no carbohydrate, while the other, C-III-3, contains 3 moles of sialic acid and 1 mole of galactosamine per mole of protein.