The recently reported amino acid sequence of rat angiotensinogen was subjected to a computer-assisted search for homology with known sequences stored in a data bank and found to be significantly related to that of plasma alpha 1-antitrypsin, itself a member of a family that includes antithrombin III and ovalbumin. An alignment of the four sequences shows indisputably the common ancestry of all four proteins.
Russell F. Doolittle (1983) studied this question.