1ril
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(New page: 200px<br /><applet load="1ril" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ril, resolution 2.8Å" /> '''CRYSTAL STRUCTURE OF ...)
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Revision as of 23:30, 20 November 2007
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CRYSTAL STRUCTURE OF RIBONUCLEASE H FROM THERMUS THERMOPHILUS HB8 REFINED AT 2.8 ANGSTROMS RESOLUTION
Overview
The crystal structure of Thermus thermophilus RNase H was determined at, 2.8 A resolution. The structure was solved by the molecular replacement, method, based on the accurately refined structure of Escherichia coli, RNase HI, which shows 52% amino acid sequence identity. Crystallographic, refinement led to an R-factor of 0.205, with a 0.019 A root-mean-square, deviation from ideal bond lengths and 0.048 A from ideal bond angle, distances. Structural comparison shows a striking similarity in the, overall folding of the thermophilic and mesophilic enzymes. The, root-mean-square displacement is 0.95 A between equivalent alpha-carbon, atoms from all elements of secondary structure (five alpha-helices and, five beta-strands). However, some notable differences, which account for, the enhanced thermostability of T. thermophilus RNase H, are observed in, loop structures and side-chain conformations. The substitution of Gly for, the left-handed helical residue (Lys95) in the E. coli enzyme is proposed, to substantially enhance the thermostability, due to the release of steric, hindrance caused by the beta-carbon atom. Furthermore, it is likely that, the expansion of an aromatic cluster, arising from the replacement of, Ile78 in the mesophilic enzyme by Phe, and the increased number of, salt-bridges additively contribute to the stability.
About this Structure
1RIL is a Single protein structure of sequence from Thermus thermophilus. Active as Ribonuclease H, with EC number 3.1.26.4 Full crystallographic information is available from OCA.
Reference
Crystal structure of ribonuclease H from Thermus thermophilus HB8 refined at 2.8 A resolution., Ishikawa K, Okumura M, Katayanagi K, Kimura S, Kanaya S, Nakamura H, Morikawa K, J Mol Biol. 1993 Mar 20;230(2):529-42. PMID:8385228
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