1m08
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Crystal structure of the unbound nuclease domain of ColE7
OverviewOverview
The bacterial toxin ColE7 contains an H-N-H endonuclease domain (nuclease, ColE7) that digests cellular DNA or RNA non-specifically in target cells, leading to cell death. In the host cell, protein Im7 forms a complex with, ColE7 to inhibit its nuclease activity. Here, we present the crystal, structure of the unbound nuclease ColE7 at a resolution of 2.1A., Structural comparison between the unbound and bound nuclease ColE7 in, complex with Im7, suggests that Im7 is not an allosteric inhibitor that, induces backbone conformational changes in nuclease ColE7, but rather one, that inhibits by blocking the substrate-binding site. There were two, nuclease ColE7 molecules in the P1 unit cell in crystals and they appeared, as a dimer related to each other by a non-crystallographic dyad symmetry., Gel-filtration and cross-linking experiments confirmed that nuclease ColE7, indeed formed dimers in solution and that the dimeric conformation was, more favored in the presence of double-stranded DNA. Structural comparison, of nuclease ColE7 with the His-Cys box homing endonuclease I-PpoI further, demonstrated that H-N-H motifs in dimeric nuclease ColE7 were oriented in, a manner very similar to that of the betabetaalpha-fold of the active, sites found in dimeric I-PpoI. A mechanism for the binding of, double-stranded DNA by dimeric H-N-H nuclease ColE7 is suggested.
About this StructureAbout this Structure
1M08 is a Single protein structure of sequence from Escherichia coli with ZN and PO4 as ligands. Full crystallographic information is available from OCA.
ReferenceReference
The crystal structure of the nuclease domain of colicin E7 suggests a mechanism for binding to double-stranded DNA by the H-N-H endonucleases., Cheng YS, Hsia KC, Doudeva LG, Chak KF, Yuan HS, J Mol Biol. 2002 Nov 22;324(2):227-36. PMID:12441102
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