title: New clues in the allosteric activation of DNA cleavage by SgrAI: structures of SgrAI bound to cleaved primary-site DNA and uncleaved secondary-site DNA.
abstract: SgrAI is a type II restriction endonuclease that cuts an unusually long recognition sequence and exhibits allosteric self-activation with expansion of DNA-sequence specificity. The three-dimensional crystal structures of SgrAI bound to cleaved primary-site DNA and Mg²(+) and bound to secondary-site DNA with either Mg²(+) or Ca²(+) are presented. All three structures show a conformation of enzyme and DNA similar to the previously determined dimeric structure of SgrAI bound to uncleaved primary-site DNA and Ca²(+) [Dunten et al. (2008), Nucleic Acids Res. 36, 5405-5416], with the exception of the cleaved bond and a slight shifting of the DNA in the SgrAI/cleaved primary-site DNA/Mg²(+) structure. In addition, a new metal ion binding site is located in one of the two active sites in this structure, which is consistent with proposals for the existence of a metal-ion site near the 3'-O leaving group.
authors.affiliation: Department of Chemistry and Biochemistry, University of Arizona, Tucson, 85721, USA.
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Little
authors.forename: Pete W
authors.initials: PW
authors.lastname: Dunten
authors.forename: Jurate
authors.initials: J
authors.lastname: Bitinaite
authors.forename: Nancy C
authors.initials: NC
authors.lastname: Horton
mesh_terms: D000494:Allosteric Regulation; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D053837:DNA Cleavage; D015252:Deoxyribonucleases, Type II Site-Specific / Q000737:chemistry* / Q000378:metabolism; D004789:Enzyme Activation; D008958:Models, Molecular; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013305:Streptomyces griseus / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D004247:DNA; C064435:endodeoxyribonuclease SgrAI; D015252:Deoxyribonucleases, Type II Site-Specific