Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 280, Issue 15, Pages 15212-15218Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M500108200
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- NIGMS NIH HHS [R01 GM069962] Funding Source: Medline
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The 3' --> 5'-exonucleases process DNA ends in many DNA repair pathways of human cells. Determination of the human TREX2 structure is the first of a dimeric 3'-deoxyribonuclease and indicates how this highly efficient nonprocessive enzyme removes nucleotides at DNA 3' termini. Symmetry in the TREX2 dimer positions the active sites at opposite outer edges providing open access for the DNA. Adjacent to each active site is a flexible region containing three arginines positioned appropriately to bind DNA and to control its entry into the active site. Mutation of these three arginines to alanines reduces the DNA binding capacity by similar to 100-fold with no effect on catalysis. The human TREX2 catalytic residues overlay with the bacterial DnaQ family of 3'-exonucleases confirming the structural conservation of the catalytic sites despite limited sequence identity, and mutations of these residues decrease the still measurable activity by similar to 10(5)-fold, confirming their catalytic role.
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