Insertion of a homing endonuclease creates a genes-in-pieces ribonucleotide reductase that retains function

摘要: In bacterial and phage genomes, coding regions are sometimes interrupted by self-splicing introns or inteins, which can encode mobility-promoting homing endonucleases. Homing endonuclease genes also found free-standing (not intron- intein-encoded) in genomes where they inserted intergenic regions. One example is the HNH family endonuclease, mobE, between large (nrdA) small (nrdB) subunit of aerobic ribonucleotide reductase (RNR) T-even phages T4, RB2, RB3, RB15, LZ7. Here, we describe an insertion mobE into nrdA gene Aeromonas hydrophila Aeh1. The creates a unique genes-in-pieces arrangement, split two independent genes, nrdA-a nrdA-b, each encoding cysteine residues that correspond to active-site uninterrupted NrdA proteins. Remarkably, does not inactivate function, although intron intein. We copurified NrdA-a, NrdA-b, NrdB proteins as complex from Aeh1-infected cells showed reconstituted has RNR activity. Class I activity Aeh1 thus assembled separate interact form composite active site, demonstrating phenotypically neutral its presence intervening sequence disrupt function surrounding gene.