EVOLUTION OF NEW-PROTEIN FUNCTION - RECOMBINATIONAL ENHANCER FIS ORIGINATED BY HORIZONTAL GENE-TRANSFER FROM THE TRANSCRIPTIONAL REGULATOR NTRC

New protein function is thought to evolve mostly by gene duplication a nd divergence. Here we present phylogenetic evidence that the multifun ctional protein Fis of the gamma proteobacterial species derived from the COOH-terminal domain of an ancestral alpha proteobacterial NtrC tr anscriptional regulatory protein. All of the known enterobacterial fis genes are preceded by an open reading frame, named yhdG, that is high ly similar to nifR3, a gene that forms an operon with ntrC in several alpha proteobacterial species, Thus, me propose that yhdG and fis mere acquired by a lineage ancestral to the gamma proteobacteria in a sing le horizontal gene transfer event, and later diverged to their present functions. (C) 1998 Federation of European Biochemical Societies.