Apolipoprotein A4 (APOA4)

APOA4 resides on chromosome 11 in close linkage to APOA1 and APOC3. APOA4 contains 3 exons separated by two introns, and is polymorphic, although most of the reported sequence polymorphisms occur in exon 3. The best validated and studied non-synonymous SNPs are a glutamine => histidine substitution at codon 380 and a threonine => serine substitution at codon 367; a sequence polymorphism has also been identified in the 3'UTR of the third exon. Intra-species comparative gene sequence analysis suggests that the APOA4 gene arose from APOA1 by gene duplication approximately 270 MYA.The primary translation product of the APOA4 gene is a 396-residue preprotein, which undergoes proteolytic processing to yield apo A-IV, a 376-reside mature O-linked glycoprotein.