1ako
From Proteopedia
EXONUCLEASE III FROM ESCHERICHIA COLI
Overview
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.
About this Structure
1AKO is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Structure and function of the multifunctional DNA-repair enzyme exonuclease III., Mol CD, Kuo CF, Thayer MM, Cunningham RP, Tainer JA, Nature. 1995 Mar 23;374(6520):381-6. PMID:7885481 Page seeded by OCA on Fri May 2 10:23:31 2008
