title: Crystal structure of RecA from Deinococcus radiodurans: insights into the structural basis of extreme radioresistance.
abstract: The resistance of Deinococcus radiodurans (Dr) to extreme doses of ionizing radiation depends on its highly efficient capacity to repair dsDNA breaks. Dr RecA, the key protein in the repair of dsDNA breaks by homologous recombination, promotes DNA strand-exchange by an unprecedented inverse pathway, in which the presynaptic filament is formed on dsDNA instead of ssDNA. In order to gain insight into the remarkable repair capacity of Dr and the novel mechanistic features of its RecA protein, we have determined its X-ray crystal structure in complex with ATPgammaS at 2.5A resolution. Like RecA from Escherichia coli, Dr RecA crystallizes as a helical filament that is closely related to its biologically relevant form, but with a more compressed pitch of 67 A. Although the overall fold of Dr RecA is similar to E.coli RecA, there is a large reorientation of the C-terminal domain, which in E.coli RecA has a site for binding dsDNA. Compared to E.coli RecA, the inner surface along the central axis of the Dr RecA filament has an increased positive electrostatic potential. Unique amino acid residues in Dr RecA cluster around a flexible beta-hairpin that has also been implicated in DNA binding.
authors.affiliation: Department of Molecular and Cellular Biochemistry, Ohio State University College of Medicine and Public Health, 371 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210, USA.
authors.forename: Rakhi
authors.initials: R
authors.lastname: Rajan
authors.forename: Charles E
authors.initials: CE
authors.lastname: Bell
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004260:DNA Repair; D034301:Deinococcus / Q000737:chemistry* / Q000528:radiation effects*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011839:Radiation, Ionizing; D011938:Rec A Recombinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D055672:Static Electricity
chemical_list: D001426:Bacterial Proteins; D000255:Adenosine Triphosphate; D011938:Rec A Recombinases