1ako: Difference between revisions

The repair of DNA requires the removal of abasic sites, which are, constantly generated in vivo both spontaneously and by enzymatic removal, of uracil, and of bases damaged by active oxygen species, alkylating, agents and ionizing radiation. The major apurinic/apyrimidinic (AP), DNA-repair endonuclease in Escherichia coli is the multifunctional enzyme, exonuclease III, which also exhibits 3'-repair diesterase, 3'-->5', exonuclease, 3'-phosphomonoesterase and ribonuclease activities. We report, here the 1.7 A resolution crystal structure of exonuclease III which, reveals a 2-fold symmetric, four-layered alpha beta fold with similarities, to both deoxyribonuclease I and RNase H. In the ternary complex determined, at 2.6 A resolution, Mn2+ and dCMP bind to exonuclease III at one end of, the alpha beta-sandwich, in a region dominated by positive electrostatic, potential. Residues conserved among AP endonucleases from bacteria to man, cluster within this active site and appear to participate in, phosphate-bond cleavage at AP sites through a nucleophilic attack, facilitated by a single bound metal ion.

1AKO is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Active as [http://en.wikipedia.org/wiki/Exodeoxyribonuclease_III Exodeoxyribonuclease III], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.1.11.2 3.1.11.2] Structure known Active Site: MG1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1AKO OCA].  

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