1ako

From Proteopedia

Revision as of 13:43, 5 November 2007

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. Active as Exodeoxyribonuclease III, with EC number 3.1.11.2 Structure known Active Site: MG1. 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

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