4rnt
From Proteopedia
(New page: 200px<br /><applet load="4rnt" size="450" color="white" frame="true" align="right" spinBox="true" caption="4rnt, resolution 2.2Å" /> '''HIS 92 ALA MUTATION I...) |
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| - | [[Image:4rnt.jpg|left|200px]]<br /><applet load="4rnt" size=" | + | [[Image:4rnt.jpg|left|200px]]<br /><applet load="4rnt" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="4rnt, resolution 2.2Å" /> | caption="4rnt, resolution 2.2Å" /> | ||
'''HIS 92 ALA MUTATION IN RIBONUCLEASE T1 INDUCES SEGMENTAL FLEXIBILITY. AN X-RAY STUDY'''<br /> | '''HIS 92 ALA MUTATION IN RIBONUCLEASE T1 INDUCES SEGMENTAL FLEXIBILITY. AN X-RAY STUDY'''<br /> | ||
==Overview== | ==Overview== | ||
| - | In the genetically mutated ribonuclease T1 His92Ala (RNase T1 His92Ala), deletion of the active site His92 imidazole leads to an inactive enzyme. | + | In the genetically mutated ribonuclease T1 His92Ala (RNase T1 His92Ala), deletion of the active site His92 imidazole leads to an inactive enzyme. Attempts to crystallize RNase T1 His92Ala under conditions used for wild-type enzyme failed, and a modified protocol produced two crystal forms, one obtained with polyethylene glycol (PEG), and the other with phosphate as precipitants. Space groups are identical to wild-type RNase T1, P2(1)2(1)2(1), but unit cell dimensions differ significantly, associated with different molecular packings in the crystals; they are a = 31.04 A, b = 62.31 A, c = 43.70 A for PEG-derived crystals and a = 32.76 A, b = 55.13 A, c = 43.29 A for phosphate-derived crystals, compared to a = 48.73 A, b = 46.39 A, c = 41.10 A for uncomplexed wild-type RNase T1. The crystal structures were solved by molecular replacement and refined by stereochemically restrained least-squares methods based on Fo greater than or equal to sigma (Fo) of 3712 reflections in the resolution range 10 to 2.2 A (R = 15.8%) for the PEG-derived crystal and based on Fo greater than or equal to sigma (Fo) of 6258 reflections in the resolution range 10 to 1.8 A (R = 14.8%) for the phosphate-derived crystal. The His92Ala mutation deletes the hydrogen bond His92N epsilon H ... O Asn99 of wild-type RNase T1, thereby inducing structural flexibility and conformational changes in the loop 91 to 101 which is located at the periphery of the globular enzyme. This loop is stabilized in the wild-type protein by two beta-turns of which only one is retained in the crystals obtained with PEG. In the crystals grown with phosphate as precipitant, both beta-turns are deleted and the segment Gly94-Ala95-Ser96-Gly97 is so disordered that it is not seen at all. In addition, the geometry of the guanine binding site in both mutant studies is different from "empty" wild-type RNase T1 but similar to that found in complexes with guanosine derivatives: the Glu46 side-chain carboxylate hydrogen bonds to Tyr42 O eta; water molecules that are present in the guanine binding site of "empty" wild-type RNase T1 are displaced; the Asn43-Asn44 peptide is flipped such that phi/psi-angles of Asn44 are in alpha L-conformation (that is observed in wild-type enzyme when guanine is bound).(ABSTRACT TRUNCATED AT 400 WORDS) |
==About this Structure== | ==About this Structure== | ||
| - | 4RNT is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Aspergillus_oryzae Aspergillus oryzae]. Active as [http://en.wikipedia.org/wiki/Ribonuclease_T(1) Ribonuclease T(1)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.1.27.3 3.1.27.3] Full crystallographic information is available from [http:// | + | 4RNT is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Aspergillus_oryzae Aspergillus oryzae]. Active as [http://en.wikipedia.org/wiki/Ribonuclease_T(1) Ribonuclease T(1)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.1.27.3 3.1.27.3] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4RNT 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 19:14:13 2008'' |
Revision as of 17:14, 21 February 2008
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HIS 92 ALA MUTATION IN RIBONUCLEASE T1 INDUCES SEGMENTAL FLEXIBILITY. AN X-RAY STUDY
Overview
In the genetically mutated ribonuclease T1 His92Ala (RNase T1 His92Ala), deletion of the active site His92 imidazole leads to an inactive enzyme. Attempts to crystallize RNase T1 His92Ala under conditions used for wild-type enzyme failed, and a modified protocol produced two crystal forms, one obtained with polyethylene glycol (PEG), and the other with phosphate as precipitants. Space groups are identical to wild-type RNase T1, P2(1)2(1)2(1), but unit cell dimensions differ significantly, associated with different molecular packings in the crystals; they are a = 31.04 A, b = 62.31 A, c = 43.70 A for PEG-derived crystals and a = 32.76 A, b = 55.13 A, c = 43.29 A for phosphate-derived crystals, compared to a = 48.73 A, b = 46.39 A, c = 41.10 A for uncomplexed wild-type RNase T1. The crystal structures were solved by molecular replacement and refined by stereochemically restrained least-squares methods based on Fo greater than or equal to sigma (Fo) of 3712 reflections in the resolution range 10 to 2.2 A (R = 15.8%) for the PEG-derived crystal and based on Fo greater than or equal to sigma (Fo) of 6258 reflections in the resolution range 10 to 1.8 A (R = 14.8%) for the phosphate-derived crystal. The His92Ala mutation deletes the hydrogen bond His92N epsilon H ... O Asn99 of wild-type RNase T1, thereby inducing structural flexibility and conformational changes in the loop 91 to 101 which is located at the periphery of the globular enzyme. This loop is stabilized in the wild-type protein by two beta-turns of which only one is retained in the crystals obtained with PEG. In the crystals grown with phosphate as precipitant, both beta-turns are deleted and the segment Gly94-Ala95-Ser96-Gly97 is so disordered that it is not seen at all. In addition, the geometry of the guanine binding site in both mutant studies is different from "empty" wild-type RNase T1 but similar to that found in complexes with guanosine derivatives: the Glu46 side-chain carboxylate hydrogen bonds to Tyr42 O eta; water molecules that are present in the guanine binding site of "empty" wild-type RNase T1 are displaced; the Asn43-Asn44 peptide is flipped such that phi/psi-angles of Asn44 are in alpha L-conformation (that is observed in wild-type enzyme when guanine is bound).(ABSTRACT TRUNCATED AT 400 WORDS)
About this Structure
4RNT is a Single protein structure of sequence from Aspergillus oryzae. Active as Ribonuclease T(1), with EC number 3.1.27.3 Full crystallographic information is available from OCA.
Reference
His92Ala mutation in ribonuclease T1 induces segmental flexibility. An X-ray study., Koellner G, Choe HW, Heinemann U, Grunert HP, Zouni A, Hahn U, Saenger W, J Mol Biol. 1992 Apr 5;224(3):701-13. PMID:1314902
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