1g15
From Proteopedia
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CO-CRYSTAL OF E. COLI RNASE HI WITH TWO MN2+ IONS BOUND IN THE THE ACTIVE SITE
Overview
Ribonuclease H (RNase H) selectively degrades the RNA strand of RNA.DNA, hybrids in a divalent cation-dependent manner. Previous structural studies, revealed a single Mg(2+) ion-binding site in Escherichia coli RNase HI. In, the crystal structure of the related RNase H domain of human, immunodeficiency virus reverse transcriptase, however, two Mn(2+) ions, were observed suggesting a different mode of metal binding. E. coli RNase, HI shows catalytic activity in the presence of Mg(2+) or Mn(2+) ions, but, these two metals show strikingly different optimal concentrations. Mg(2+), ions are required in millimolar concentrations, but Mn(2+) ions are only, required in micromolar quantities. Based upon the metal dependence of E., coli RNase HI activity, we proposed an activation/attenuation model in, which one metal is required for catalysis, and binding of a second metal, is inhibitory. We have now solved the co-crystal structure of E. coli, RNase HI with Mn(2+) ions at 1.9-A resolution. Two octahedrally, coordinated Mn(2+) ions are seen to bind to the enzyme-active site., Residues Asp-10, Glu-48, and Asp-70 make direct (inner sphere), coordination contacts to the first (activating) metal, whereas residues, Asp-10 and Asp-134 make direct contacts to the second (attenuating) metal., This structure is consistent with biochemical evidence suggesting that two, metal ions may bind RNase H but liganding a second ion inhibits RNase H, activity.
About this Structure
1G15 is a Single protein structure of sequence from Escherichia coli with MN as ligand. Active as Ribonuclease H, with EC number 3.1.26.4 Full crystallographic information is available from OCA.
Reference
Co-crystal of Escherichia coli RNase HI with Mn2+ ions reveals two divalent metals bound in the active site., Goedken ER, Marqusee S, J Biol Chem. 2001 Mar 9;276(10):7266-71. Epub 2000 Nov 16. PMID:11083878
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