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| [[Image:1zns.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_1zns| PDB=1zns | SCENE= }} | | {{STRUCTURE_1zns| PDB=1zns | SCENE= }} |
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| '''Crystal structure of N-ColE7/12-bp DNA/Zn complex'''
| | ===Crystal structure of N-ColE7/12-bp DNA/Zn complex=== |
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| ==Overview==
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| The nuclease domain of ColE7 (N-ColE7) contains an H-N-H motif that folds in a beta beta alpha-metal topology. Here we report the crystal structures of a Zn2+-bound N-ColE7 (H545E mutant) in complex with a 12-bp duplex DNA and a Ni2+-bound N-ColE7 in complex with the inhibitor Im7 at a resolution of 2.5 A and 2.0 A, respectively. Metal-dependent cleavage assays showed that N-ColE7 cleaves double-stranded DNA with a single metal ion cofactor, Ni2+, Mg2+, Mn2+, and Zn2+. ColE7 purified from Escherichia coli contains an endogenous zinc ion that was not replaced by Mg2+ at concentrations of <25 mM, indicating that zinc is the physiologically relevant metal ion in N-ColE7 in host E. coli. In the crystal structure of N-ColE7/DNA complex, the zinc ion is directly coordinated to three histidines and the DNA scissile phosphate in a tetrahedral geometry. In contrast, Ni2+ is bound in N-ColE7 in two different modes, to four ligands (three histidines and one phosphate ion), or to five ligands with an additional water molecule. These data suggest that the divalent metal ion in the His-metal finger motif can be coordinated to six ligands, such as Mg2+ in I-PpoI, Serratia nuclease and Vvn, five ligands or four ligands, such as Ni2+ or Zn2+ in ColE7. Universally, the metal ion in the His-metal finger motif is bound to the DNA scissile phosphate and serves three roles during hydrolysis: polarization of the P-O bond for nucleophilic attack, stabilization of the phosphoanion transition state and stabilization of the cleaved product. | | The line below this paragraph, {{ABSTRACT_PUBMED_16434744}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 16434744 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_16434744}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: His-metal finger]] | | [[Category: His-metal finger]] |
| [[Category: Protein-dna complex]] | | [[Category: Protein-dna complex]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 17:51:18 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 09:24:58 2008'' |