Common structural organization of the angiotensinogen and the alpha 1-antitrypsin genes

A rat genomic DNA segment containing the angiotensinogen gene has been isolated from a gene library by hybridization with a restriction fragment derived from a previously cloned cDNA for rat angiotensinogen. Restriction mapping and nucleotide sequence analysis of the cloned DNA fragments have indicated that the rat angiotensinogen gene is approximately 11.8 kilobase pairs long and consists of five exons separated by four introns. Because it has recently been reported that the sequence of angiotensinogen significantly resembles those of alpha 1-antitrypsin and ovalbumin and also that the exon-intron arrangements of the alpha 1-antitrypsin and ovalbumin genes are completely different, this study compares the structural organization of the angiotensinogen gene with those of the alpha 1-antitrypsin gene and the ovalbumin gene. The comparison has revealed that the four introns of the angiotensinogen gene are all located at the positions equivalent to or corresponding to those observed in the alpha 1-antitrypsin gene, suggesting that the angiotensinogen gene and the alpha 1-antitrypsin gene have diverged from a common ancestor gene. This finding raises interesting possibilities regarding the biological function of angiotensinogen and the evolution of the angiotensinogen gene.