Molecular basis of a unique African Variant (A-IV 5) of human apolipoprotein A-IV and its significance in lipid metabolism

✍ Scribed by M. Ilyas Kamboh; Edward R. Williams; John C. Law; Christopher E. Aston; Clareann H. Bunker; Robert E. Ferrell; William S. Pollitzer

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 724 KB
• Volume: 9
• Category: Article
• ISSN: 0741-0395
• DOI: 10.1002/gepi.1370090602

✦ Synopsis

Human apolipoprotein A-IV (apoA-IV) exhibits a genetically determined structural polymorphism amenable to analysis by isoelectric focusing and immunoblotting techniques. We have determined the allele frequency and molecular basis of a unique ApoA-ZV*S allele which is widely distributed among blacks but is absent in other populations. The frequency of the ApoA-IV*S allele in blacks (N = 308) was estimated to be 3.2%. In comparison to the common ApoA-IV*l allele, analysis of coding and non-coding sequences of the ApoA-IV*S allele revealed an in-frame insertion of 12 nucleotides near the carboxyl terminal region of the mature protein.

The insertion involves an exact duplication of the second of the four repeats and codes for 4 amino acids glutamic acid (GAA), glutamine (CAG), glutamine (CAG), and glutamine (CAG) and is responsible for the charge shift of the the apoA-IV 5 isoform slightly toward the anode as compared to the wild type apoA-IV 1 isoform on the isoelectric focusing gel. This in-frame insertion occurs in a region which is highly conserved among rat, mouse, and humans. In addition to the 12 nucleotide insertion, the four individuals sequenced for the ApoA-ZV*S allele also revealed a same-sense mutation by replacing G to T at the third position of codon 316. Our preliminary data suggest that this unqiue black allele marker may be of potentially significance in studies of human lipid metabolism and in microevolution.