EXON SHUFFLING AND OTHER WAYS OF MODULE EXCHANGE

Thanks to recent improvements in techniques used for the detection of homologies, it is now clear that module exchange played a major role i n protein evolution. Analysis of the genes of various modular proteins has identified a large number of cases where gene assembly was facili tated by intronic recombination - i.e., the proteins were formed by ex on shuffling. Studies of the principles and mechanistic details of exo n shuffling, however, revealed that this powerful evolutionary mechani sm could become significant only after the appearance of spliceosomal introns typical of higher eukaryotes. Although exon shuffling is the m ost efficient way of constructing modular proteins, recent studies on the evolution of multidomain proteins of prokaryotes emphasize that in tronic recombination is not an absolute prerequisite of module exchang e.