DIFFERENT EVOLUTIONARY HISTORIES OF KRINGLE AND PROTEASE DOMAINS IN SERINE PROTEASES - A TYPICAL EXAMPLE OF DOMAIN EVOLUTION

With the aim of elucidating the evolutionary processes of the kringle and protease domains in serine proteases which are involved with the s ystem of blood coagulation and fibrinolysis, we constructed phylogenet ic trees for the kringle and protease domains, separately, by use of a mino acid sequence data. The phylogenetic trees constructed clearly sh owed that the topologies were different between the kringle and protea se domains. Because both domains are coded by single peptides of serin e proteases, this strongly suggests that the kringle and protease doma ins must have undergone different evolutionary processes. Thus, these observations imply that serine proteases evolve in a way such that eac h domain is a unit of evolution, exemplifying a typical mode of domain evolution. A possible relationship between the domain evolution and t he exon shuffling theory is also discussed from the viewpoint of gene evolution.