Home A 2′-methyl or 2′-methylene group at G+1 in precursor tRNA interferes with Mg2+ binding at the enzyme-substrate interface in E-S complexes of E. coli RNase P
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A 2′-methyl or 2′-methylene group at G+1 in precursor tRNA interferes with Mg2+ binding at the enzyme-substrate interface in E-S complexes of E. coli RNase P

  • Simona Cuzic and Roland K. Hartmann
Published/Copyright: July 1, 2007
Biological Chemistry
From the journal Volume 388 Issue 7

Abstract

We analyzed processing of precursor tRNAs carrying a single 2′-deoxy, 2′-OCH3, or locked nucleic acid (LNA) modification at G+1 by Escherichia coli RNase P RNA in the absence and presence of its protein cofactor. The extra methyl or methylene group caused a substrate binding defect, which was rescued at higher divalent metal ion (M2+) concentrations (more efficiently with Mn2+ than Mg2+), and had a minor effect on cleavage chemistry at saturating M2+ concentrations. The 2′-OCH3 and LNA modification at G+1 resulted in higher metal ion cooperativity for substrate binding to RNase P RNA without affecting cleavage site selection. This indicates disruption of an M2+ binding site in enzyme-substrate complexes, which is compensated for by occupation of alternative M2+ binding sites of lower affinity. The 2′-deoxy modification at G+1 caused at most a two-fold decrease in the cleavage rate; this mild defect relative to 2′-OCH3 and LNA at G+1 indicates that the defect caused by the latter two is steric in nature. We propose that the 2′-hydroxyl at G+1 in the substrate is in the immediate vicinity of the M2+ cluster at the phosphates of A67 to U69 in helix P4 of E. coli RNase P RNA.


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Received: 2007-3-2
Accepted: 2007-4-19
Published Online: 2007-07-01

©2007 by Walter de Gruyter Berlin New York

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