1mz8

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spinqualitylabelsall models 1mz8, resolution 2.00Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

CRYSTAL STRUCTURES OF THE NUCLEASE DOMAIN OF COLE7/IM7 IN COMPLEX WITH A PHOSPHATE ION AND A ZINC ION

Overview

H-N-H is a motif found in the nuclease domain of a subfamily of bacteria, toxins, including colicin E7, that are capable of cleaving DNA, nonspecifically. This H-N-H motif has also been identified in a subfamily, of homing endonucleases, which cleave DNA site specifically. To better, understand the role of metal ions in the H-N-H motif during DNA, hydrolysis, we crystallized the nuclease domain of colicin E7, (nuclease-ColE7) in complex with its inhibitor Im7 in two different, crystal forms, and we resolved the structures of EDTA-treated, Zn(2+)-bound and Mn(2+)-bound complexes in the presence of phosphate ions, at resolutions of 2.6 A to 2.0 A. This study offers the first, determination of the structure of a metal-free and substrate-free enzyme, in the H-N-H family. The H-N-H motif contains two antiparallel, beta-strands linked to a C-terminal alpha-helix, with a divalent metal ion, located in the center. Here we show that the metal-binding sites in the, center of the H-N-H motif, for the EDTA-treated and Mg(2+)-soaked complex, crystals, were occupied by water molecules, indicating that an alkaline, earth metal ion does not reside in the same position as a transition metal, ion in the H-N-H motif. However, a Zn(2+) or Mn(2+) ions were observed in, the center of the H-N-H motif in cases of Zn(2+) or Mn(2+)-soaked, crystals, as confirmed in anomalous difference maps. A phosphate ion was, found to bridge between the divalent transition metal ion and His545., Based on these structures and structural comparisons with other nucleases, we suggest a functional role for the divalent transition metal ion in the, H-N-H motif in stabilizing the phosphoanion in the transition state during, hydrolysis.

About this Structure

1MZ8 is a Protein complex structure of sequences from Escherichia coli with ZN and PO4 as ligands. Full crystallographic information is available from OCA.

Reference

Metal ions and phosphate binding in the H-N-H motif: crystal structures of the nuclease domain of ColE7/Im7 in complex with a phosphate ion and different divalent metal ions., Sui MJ, Tsai LC, Hsia KC, Doudeva LG, Ku WY, Han GW, Yuan HS, Protein Sci. 2002 Dec;11(12):2947-57. PMID:12441392

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