Open AccessNew clues in the allosteric activation of DNA cleavage by Sgr AI: structures of Sgr AI bound to cleaved primary‐site DNA and uncleaved secondary‐site DNA
Author(s) -
Little Elizabeth J.,
Dunten Pete W.,
Bitinaite Jurate,
Horton Nancy C.
Publication year - 2011
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444910047785
Subject(s) - dna , active site , binding site , restriction enzyme , cleavage (geology) , protein secondary structure , chemistry , nucleic acid secondary structure , allosteric regulation , dna binding site , nucleic acid , recognition sequence , stereochemistry , microbiology and biotechnology , biology , crystallography , enzyme , biochemistry , rna , gene , paleontology , fracture (geology) , gene expression , promoter
Sgr AI 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 Sgr AI bound to cleaved primary‐site DNA and Mg 2+ and bound to secondary‐site DNA with either Mg 2+ or Ca 2+ are presented. All three structures show a conformation of enzyme and DNA similar to the previously determined dimeric structure of Sgr AI bound to uncleaved primary‐site DNA and Ca 2+ [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 Sgr AI/cleaved primary‐site DNA/Mg 2+ 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.