Annexin I (AnxI) is a calcium-dependent membrane binding protein which has been implicated in various physiological activities. The region of the chicken anxI cDNA encoding the first 130 amino terminal residues was cloned by reverse transcription PCR in order to determine the relationship of its variable ammo-terminal regulatory region with other known annexins. This nucleotide sequence shows 86% identity with pigeon Anxl isoforms, and 57% with its human homolog. The protein encoded by the chicken anxI cDNA lacks the canonical epidermal growth factor receptor/kinase phosphorylation site, which is present in Anxl of other species. In contrast, the putative protein kinase C phosphorylation site of the amino-tenninus is present in the chicken AnxI. Whereas the pigeon genome contains two anxI genes, genomic Southern analysis shows that in the chicken Anxl is encoded by only a single gene. These data suggest that AnxI has undergone significant sequence variation in the avians, and clarifies the relationships of the avian anxI genes with their ancestral homologs.
