MOLECULAR-CLONING AND SEQUENCE-ANALYSIS OF CDNA-ENCODING PLASMA ALPHA-1-ANTIPROTEINASE FROM SYRIAN-HAMSTER - IMPLICATIONS FOR THE EVOLUTIONOF RODENTIA

Complementary DNA clones encoding plasma alpha-1-antiproteinase (also called alpha-1-antitrypsin or alpha-1-proteinase inhibitor) were isola ted from Syrian hamster liver cDNA library and sequenced. The deduced amino acid sequence of putative reactive site (P3-P'3) was Ile-Pro-Met -Ser-Val-Pro, characteristic of alpha-1-antiproteinase of orthodox typ e (Suzuki, Y. et al. (1991) J. Biol. Chem. 266, 928-932). A molecular phylogenetic tree of all known orthologous proteins was constructed ba sed on the synonymous substitution rate. The result shows that the ham ster has branched off first before the divergence among mice, rats, an d gerbils, and that the rabbit is the closest relative of the guinea p ig which is separated from the rodents. Although this tree differs lar gely from the classical phylogeny based on the morphology (hamsters an d gerbils belong to the same family, Cricetidae, and the guinea pig be longs to the order Rodentia), it lends support to recent concepts that the hamster and guinea pig differ, in a number of biochemical feature s, not only from each other but also from mice and rats, and that the guinea pig may belong to an order distinct from Rodentia.