BIOLOGICAL CHARACTERIZATION OF TWO PUTATIVE DNA METABOLISM ENZYMES IN DEINOCOCCUS RADIODURANS
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HerA proteins are members of the FtsK-HerA superfamily of P-loop ATPases. FtsK is a bacterial protein that translocates double-stranded DNA during cell division. In archaea, herA is an essential gene that encodes an enzyme believed to be important for recombinational DNA repair. It is typically found in an operon with a gene that codes for a nuclease, nurA. Homologs of herA and nurA are found in a few bacterial genomes. In most cases, these bacteria lack an ftsK homolog. The functions of NurA and HerA in bacteria are not known. We chose to investigate the roles of NurA and HerA in Deinococcus radiodurans, typically studied for its extreme resistance to double-strand DNA breaks. The D. radiodurans genome has homologs of nurA and herA in an operon, and it also has an ftsK gene. We made strains with deletions of either herA or nurA and characterized their sensitivity to DNA damaging agents and basic growth properties. The results indicate that neither gene is essential in D. radiodurans, and deletions of the genes do not cause significant sensitivity to DNA damaging agents. The herA deletion strain displayed a distinct phenotype consisting of slower growth and larger cell types. The herA phenotype in D. radiodurans is similar to that of mutation of ftsK homologs in Escherichia coli and Bacillus subtilis. The results suggest that HerA has an FtsK-like function in cell division, rather than acting in DNA repair, in D. radiodurans.