1ril
From Proteopedia
(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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| - | [[Image:1ril.jpg|left|200px]]<br /><applet load="1ril" size=" | + | [[Image:1ril.jpg|left|200px]]<br /><applet load="1ril" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1ril, resolution 2.8Å" /> | caption="1ril, resolution 2.8Å" /> | ||
'''CRYSTAL STRUCTURE OF RIBONUCLEASE H FROM THERMUS THERMOPHILUS HB8 REFINED AT 2.8 ANGSTROMS RESOLUTION'''<br /> | '''CRYSTAL STRUCTURE OF RIBONUCLEASE H FROM THERMUS THERMOPHILUS HB8 REFINED AT 2.8 ANGSTROMS RESOLUTION'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The crystal structure of Thermus thermophilus RNase H was determined at | + | 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== | ==About this Structure== | ||
| - | 1RIL is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Thermus_thermophilus Thermus thermophilus]. Active as [http://en.wikipedia.org/wiki/Ribonuclease_H Ribonuclease H], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.1.26.4 3.1.26.4] Full crystallographic information is available from [http:// | + | 1RIL is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Thermus_thermophilus Thermus thermophilus]. Active as [http://en.wikipedia.org/wiki/Ribonuclease_H Ribonuclease H], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.1.26.4 3.1.26.4] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1RIL OCA]. |
==Reference== | ==Reference== | ||
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[[Category: hydrolase(endoribonuclease)]] | [[Category: hydrolase(endoribonuclease)]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:51:15 2008'' |
Revision as of 12:51, 21 February 2008
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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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