Molecular cloning of a human apoC-III variant: Thr 74----Ala 74 mutation prevents O-glycosylation.
Apolipoprotein C-III (apoC-III) is a major protein of very low density lipoprotein (VLDL). The apoC-III polypeptide contains a carbohydrate chain containing galactosamine, galactose, and sialic acid attached in O-linkage to a threonine residue at position 74. We have cloned the apoC-III gene from a subject whose serum contained unusually high amounts of apoC-III lacking the carbohydrate moiety (C-III-0). DNA sequence analysis of the cloned gene revealed a single nucleotide substitution (A----G) that encodes an alanine at position 74 instead of the normal threonine. As a result of this amino acid replacement, the mutant apoC-III polypeptide is not glycosylated. The mutation in the apoC-III gene creates a novel AluI site that permits diagnosis of the change by Southern blotting of genomic DNA.
D000409:Alanine; D000595:Amino Acid Sequence; D053305:Apolipoprotein C-III; D001056:Apolipoproteins C / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000032:analysis; D006031:Glycosylation; D006801:Humans; D008079:Lipoproteins, VLDL / Q000097:blood; D008969:Molecular Sequence Data; D009154:Mutation; D013912:Threonine
D053305:Apolipoprotein C-III; D001056:Apolipoproteins C; D008079:Lipoproteins, VLDL; D013912:Threonine; D004247:DNA; D000409:Alanine