1rda
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(New page: 200px<br /><applet load="1rda" size="450" color="white" frame="true" align="right" spinBox="true" caption="1rda, resolution 2.15Å" /> '''CRYSTAL STRUCTURES O...)
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Revision as of 23:21, 20 November 2007
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CRYSTAL STRUCTURES OF RIBONUCLEASE HI ACTIVE SITE MUTANTS FROM ESCHERICHIA COLI
Overview
In order to investigate the relationships between the three-dimensional, structure and the enzymic activity of E. coli RNase HI, three mutant, proteins, which were completely inactivated by the replacements of three, functional residues, Asp10 by Asn (D10N), Glu48 by Gln (E48Q), and Asp70, by Asn (D70N), were crystallized. Their three-dimensional structures were, determined by x-ray crystallography. Although the entire backbone, structures of these mutants were not affected by the replacements, very, localized conformational changes were observed around the Mg(2+)-binding, site. The substitution of an amide group for a negatively charged carboxyl, group in common induces the formation of new hydrogen bond networks, presumably due to the cancellation of repulsive forces between carboxyl, side chains with negative charges. These conformational changes can, account for the loss of the enzymic activity in the mutants, and suggest a, possible role for Mg2+ in the hydrolysis. Since the 3 replaced acidic, residues are completely conserved in sequences of reverse transcriptases, from retroviruses, including human immunodeficiency virus, the concepts of, the catalytic mechanism deduced from this structural analysis can also be, applied to RNase H activity in reverse transcriptases.
About this Structure
1RDA is a Single protein structure of sequence from Escherichia coli. Active as Ribonuclease H, with EC number 3.1.26.4 Full crystallographic information is available from OCA.
Reference
Crystal structures of ribonuclease HI active site mutants from Escherichia coli., Katayanagi K, Ishikawa M, Okumura M, Ariyoshi M, Kanaya S, Kawano Y, Suzuki M, Tanaka I, Morikawa K, J Biol Chem. 1993 Oct 15;268(29):22092-9. PMID:8408067
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