Wallaby serum amyloid A protein: cDNA cloning, sequence and evolutionary analysis

A serum amyloid A (SAA) clone was isolated from a Tammar wallaby cDNA library, the most distantly related mammalian species for which an SAA has been described to date. The clone predicts a premolecule of 127 amino acids with good homology to other mammalian SAAs, and consists of an 18 residue leader peptide and a mature protein of 109 amino acids. Evolutionary analysis at both the protein and nucleotide level indicate that the wallaby SAA clone clusters with the acute phase SAAs. However, as the SAA superfamily has undergone concerted evolution it is not possible to determine at this point which acute phase SAA it is most like. The grouping of wallaby SAA inside the acute phase SAA cluster demonstrates that at least some of the duplication events giving rise to multiple acute phase genes occurred prior to the divergence of the eutherian and metatherian mammals.