Identity of Chimpanzee with Human Fibrinopeptides

Abstract

FIBRINOPEPTIDES, those portions of vertebrate fibrinogen molecules split off by thrombin during clotting, exhibit a very large degree of interspecific variability. The amino-acid sequences of these peptides have been determined for more than thirty different species of mammals, and the number of identified amino-acid replacements ranks the fibrinopeptides among the most variable polypeptide structures known. On the arbitrary scale developed by Dayhoff¹ these molecules have a variability index of 90, compared with values of 13 and 11 for the β and α chains of haemoglobin, and a score of 3 for cytochrome c. As a result of this propensity for rapid change, the fibrinopeptides are particularly useful for tracing phylogenetic relationships at the generic level.