Amino acid sequence of human prothrombin fragments 1 and 2.

Abstract

The amino acid sequence of the nonthrombin half of human prothrombin is presented. Prothrombin fragment 1 had 155 amino acid residues as compared with 156 for the bovine equivalent. Ten .gamma.-carboxyglutamic acid residues are at the same location in each species, Human prothrombin fragment 2 contains 118 amino acid residues, as does the similar bovine fragment. Comparing bovine and human prothrombin fragment 1, 131 residues were identical (94%). In prothrombin fragment 2, 84 residues were identical (71%). Assuming a time span of 90 million yr since the radiation of several orders of placental mammals, prothrombin fragments 1 and 2 incorporated 1 substitution site per 100 amino acid sites every 11.2 and 6.3 million yr, respectively. Internal homology is ascribed to partial gene duplication, with the most lilely crossover point located between residues 60-61 and residues 165-166.