1m0i
From Proteopedia
Revision as of 19:09, 30 March 2008
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| , resolution 2.55Å | |||||||
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| Ligands: | |||||||
| Gene: | Endonuclease I (Enterobacteria phage T7) | ||||||
| Activity: | Deoxyribonuclease IV (phage-T(4)-induced), with EC number 3.1.21.2 | ||||||
| Related: | 1FZR, 1M0D
| ||||||
| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
Crystal Structure of Bacteriophage T7 Endonuclease I with a Wild-Type Active Site
Overview
T7 endonuclease I is a nuclease that is selective for the structure of the four-way DNA junction. The active site is similar to those of a number of restriction enzymes. We have solved the crystal structure of endonuclease I with a wild-type active site. Diffusion of manganese ions into the crystal revealed two peaks of electron density per active site, defining two metal ion-binding sites. Site 1 is fully occupied, and the manganese ion is coordinated by the carboxylate groups of Asp55 and Glu65, and the main chain carbonyl of Thr66. Site 2 is partially occupied, and the metal ion has a single protein ligand, the remaining carboxylate oxygen atom of Asp55. Isothermal titration calorimetry showed the sequential exothermic binding of two manganese ions in solution, with dissociation constants of 0.58 +/- 0.019 and 14 +/- 1.5 mM. These results are consistent with a two metal ion mechanism for the cleavage reaction, in which the hydrolytic water molecule is contained in the first coordination sphere of the site 1-bound metal ion.
About this Structure
1M0I is a Single protein structure of sequence from Enterobacteria phage t7. Full crystallographic information is available from OCA.
Reference
Metal ions bound at the active site of the junction-resolving enzyme T7 endonuclease I., Hadden JM, Declais AC, Phillips SE, Lilley DM, EMBO J. 2002 Jul 1;21(13):3505-15. PMID:12093751
Page seeded by OCA on Sun Mar 30 22:09:38 2008
