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1xo1

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{{STRUCTURE_1xo1| PDB=1xo1 | SCENE= }}
{{STRUCTURE_1xo1| PDB=1xo1 | SCENE= }}
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'''T5 5'-EXONUCLEASE MUTANT K83A'''
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===T5 5'-EXONUCLEASE MUTANT K83A===
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==Overview==
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Efficient cellular DNA replication requires the activity of a 5'-3' exonuclease. These enzymes are able to hydrolyze DNA.DNA and RNA.DNA substrates exonucleolytically, and they are structure-specific endonucleases. The 5'-3' exonucleases are conserved in organisms as diverse as bacteriophage and mammals. Crystal structures of three representative enzymes identify two divalent-metal-binding sites typically separated by 8-10 A. Site-directed mutagenesis was used to investigate the roles of three lysine residues (K83, K196, and K215) situated near two metal-binding sites in bacteriophage T5 5'-3' exonuclease. Neither K196 nor K215 was essential for either the exo- or the endonuclease activity, but mutation of these residues increased the dissociation constant for the substrate from 5 nM to 200 nM (K196A) and 50 nM (K215A). Biochemical analysis demonstrated that K83 is absolutely required for exonucleolytic activity on single-stranded DNA but is not required for endonucleolytic cleavage of flap structures. Structural analysis of this mutant by x-ray crystallography showed no significant perturbations around the metal-binding sites in the active site. The wild-type protein has different pH optima for endonuclease and exonuclease activities. Taken together, these results suggest that different mechanisms for endo- and exonucleolytic hydrolysis are used by this multifunctional enzyme.
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(as it appears on PubMed at http://www.pubmed.gov), where 9874768 is the PubMed ID number.
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{{ABSTRACT_PUBMED_9874768}}
==About this Structure==
==About this Structure==
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[[Category: Hydrolase]]
[[Category: Hydrolase]]
[[Category: Nuclease]]
[[Category: Nuclease]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 15:16:57 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 19:44:55 2008''

Revision as of 16:44, 28 July 2008

Image:1xo1.png

Template:STRUCTURE 1xo1

T5 5'-EXONUCLEASE MUTANT K83A

Template:ABSTRACT PUBMED 9874768

About this Structure

1XO1 is a Single protein structure of sequence from Enterobacteria phage t5. Full crystallographic information is available from OCA.

Reference

Mutagenesis of conserved lysine residues in bacteriophage T5 5'-3' exonuclease suggests separate mechanisms of endo-and exonucleolytic cleavage., Garforth SJ, Ceska TA, Suck D, Sayers JR, Proc Natl Acad Sci U S A. 1999 Jan 5;96(1):38-43. PMID:9874768

Page seeded by OCA on Mon Jul 28 19:44:55 2008

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