Role of Archaeal HerA Protein in the Biology of the Bacterium Thermus thermophilus.

Intense gene flux between prokaryotes result in high percentage of archaeal genes in the genome of the thermophilic bacteria spp. Among these archaeal genes a homolog to the spp. HerA protein appears in all of the spp. strains so far sequenced (HepA). The role of HepA in HB27 has been analyzed using deletion mutants, and its structure resolved at low resolution by electron microscopy. Recombinant HepA shows DNA-dependent ATPase activity and its structure revealed a double ring, conically-shaped hexamer with an upper diameter of 150 Å and a bottom module of 95 Å. A central pore was detected in the structure that ranges from 13 Å at one extreme, to 30 Å at the other. Mutants lacking HepA show defective natural competence and DNA donation capability in a conjugation-like process termed "transjugation", and also high sensitivity to UV and dramatic sensitivity to high temperatures. These data support that acquisition of an ancestral archaeal HerA has been fundamental for the adaptation of spp. to high temperatures.