The Complete Amino Acid Sequence of Alanine Apolipoprotein (apoC-III), an Apolipoprotein from Human Plasma Very Low Density Lipoproteins

Abstract

Abstract The alanine apolipoprotein (apoLp-Ala) was isolated from patients with familial hyperlipoproteinemia (type V). ApoLp-Ala is a single chain protein of 79 amino acids with a single carbohydrate side chain containing 1 mole each of galactosamine and galactose, and 0 to 2 moles of sialic acid per mole of protein. The complete amino acid sequence of apoLp-Ala was determined by manual and automated Edman degradations of the intact protein, and tryptic and succinylated tryptic peptides. The NH2-terminal residue is serine, the COOH-terminal residue alanine. The carbohydrate moiety is attached to threonine at position 74 in the sequence. The amino acid sequence of apoLp-Ala contains no long sequences of hydrophobic residues which contrasts with the linear amphipathic regions present in the two integral membrane proteins cytochrome b5 and glycophorin.