The Primary Structure of Apolipoprotein-Serine

Abstract

Abstract Apolipoprotein-serine (apoLP-Ser or apoC-I) is one of the apoprotein constituents of human plasma very low density lipoprotein. The protein has 57 amino acid residues, including one residue of methionine and is lacking histidine, cysteine, cystine, and tyrosine. The NH2 terminus of apoLP-Ser is threonine and the COOH terminus is serine. Cleavage of apoLP-Ser with cyanogen bromide, followed by chromatography of the digest on Bio-Gel P-30 in 25% formic acid, yielded two fragments corresponding to the NH2-terminal (CNBr I) and the COOH-terminal (CNBr II) fragments and accounting for the 57 residues of the intact protein. The amino acid sequences of the tryptic peptides from CNBr I and chymotryptic peptides from CNBr II were determined by conventional methods. The amino acid sequence of apoLP-Ser is as follows: Thr-Pro-Asp-Val-Ser-Ser-Ala-Leu-Asp-Lys-Leu-Lys-Glu-Phe-Gly-Asn-Thr-Leu-Glu-Asp-Lys-Ala-Arg-Glu-Leu-Ile-Ser-Arg-Ile-Lys-Gln-Ser-Glu-Leu-Ser-Ala-Lys-Met-Arg-Glu-Trp-Phe-Ser-Glu-Thr-Phe-Gln-Lys-Val-Lys-Glu-Lys-Leu-Lys-Ile-Asp-Ser.