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The nuclease a-inhibitor complex is characterized by a novel metal ion bridge.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 2007 Feb 23; Vol. 282 (8), pp. 5682-90. Date of Electronic Publication: 2006 Nov 30. - Publication Year :
- 2007
-
Abstract
- Nonspecific, extracellular nucleases have received enhanced attention recently as a consequence of the critical role that these enzymes can play in infectivity by overcoming the host neutrophil defense system. The activity of the cyanobacterial nuclease NucA, a member of the betabetaalpha Me superfamily, is controlled by the specific nuclease inhibitor, NuiA. Here we report the 2.3-A resolution crystal structure of the NucA-NuiA complex, showing that NucA inhibition by NuiA involves an unusual divalent metal ion bridge that connects the nuclease with its inhibitor. The C-terminal Thr-135(NuiA) hydroxyl oxygen is directly coordinated with the catalytic Mg(2+) of the nuclease active site, and Glu-24(NuiA) also extends into the active site, mimicking the charge of a scissile phosphate. NuiA residues Asp-75 and Trp-76 form a second interaction site, contributing to the strength and specificity of the interaction. The crystallographically defined interface is shown to be consistent with results of studies using site-directed NuiA mutants. This mode of inhibition differs dramatically from the exosite mechanism of inhibition seen with the DNase colicins E7/E9 and from other nuclease-inhibitor complexes that have been studied. The structure of this complex provides valuable insights for the development of inhibitors for related nonspecific nucleases that share the DRGH active site motif such as the Streptococcus pneumoniae nuclease EndA, which mediates infectivity of this pathogen, and mitochondrial EndoG, which is involved in recombination and apoptosis.
- Subjects :
- Amino Acid Motifs genetics
Bacterial Proteins antagonists & inhibitors
Bacterial Proteins genetics
Binding Sites genetics
Cations, Divalent chemistry
Crystallography, X-Ray
Cyanobacteria chemistry
Cyanobacteria genetics
Deoxyribonucleases antagonists & inhibitors
Deoxyribonucleases genetics
Endodeoxyribonucleases antagonists & inhibitors
Endodeoxyribonucleases chemistry
Endodeoxyribonucleases genetics
Membrane Proteins antagonists & inhibitors
Membrane Proteins chemistry
Membrane Proteins genetics
Protein Structure, Quaternary
Streptococcus pneumoniae chemistry
Streptococcus pneumoniae genetics
Structural Homology, Protein
Bacterial Proteins chemistry
Deoxyribonucleases chemistry
Enzyme Inhibitors chemistry
Magnesium chemistry
Models, Molecular
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 282
- Issue :
- 8
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 17138564
- Full Text :
- https://doi.org/10.1074/jbc.M605986200