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1i45

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[[Image:1i45.gif|left|200px]]
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{{STRUCTURE_1i45| PDB=1i45 | SCENE= }}
{{STRUCTURE_1i45| PDB=1i45 | SCENE= }}
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'''YEAST TRIOSEPHOSPHATE ISOMERASE (MUTANT)'''
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===YEAST TRIOSEPHOSPHATE ISOMERASE (MUTANT)===
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==Overview==
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Product release is partially rate determining in the isomerization reaction catalyzed by Triosephosphate Isomerase, the conversion of dihydroxyacetone phosphate to D-glyceraldehyde 3-phosphate, probably because an active-site loop movement is necessary to free the product from confinement in the active-site. The timescale of the catalytic loop motion and of ligand release were studied using 19F and 31P solution-state NMR. A 5'-fluorotryptophan was incorporated in the loop N-terminal hinge as a reporter of loop motion timescale. Crystallographic studies confirmed that the structure of the fluorinated enzyme is indistinguishable from the wild-type; the fluorine accepts a hydrogen bond from water and not from a protein residue, with minimal perturbation to the flexible loop stability. Two distinct loop conformations were observed by 19F NMR. Both for unligated (empty) and ligated enzyme samples a single species was detected, but the chemical shifts of these two distinct species differed by 1.2 ppm. For samples in the presence of subsaturating amounts of a substrate analogue, glycerol 3-phosphate, both NMR peaks were present, with broadened lineshapes at 0 degrees C. In contrast, a single NMR peak representing a rapid average of the two species was observed at 30 degrees C. We conclude that the rate of loop motion is less than 1400 s(-1) at 0 degrees C and more than 1400 s(-1) at 30 degrees C. Ligand release was studied under similar sample conditions, using 31P NMR of the phosphate group of the substrate analogue. The rate of ligand release is less than 1000 s(-1) at 0 degrees C and more than 1000 s(-1) at 30 degrees C. Therefore, loop motion and product release are probably concerted and likely to represent a rate limiting step for chemistry.
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(as it appears on PubMed at http://www.pubmed.gov), where 11419952 is the PubMed ID number.
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{{ABSTRACT_PUBMED_11419952}}
==About this Structure==
==About this Structure==
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[[Category: Triosephosphate isomerase]]
[[Category: Triosephosphate isomerase]]
[[Category: Yeast]]
[[Category: Yeast]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 19:33:04 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 10:23:22 2008''

Revision as of 07:23, 1 July 2008

Image:1i45.png

Template:STRUCTURE 1i45

YEAST TRIOSEPHOSPHATE ISOMERASE (MUTANT)

Template:ABSTRACT PUBMED 11419952

About this Structure

1I45 is a Single protein structure of sequence from Saccharomyces cerevisiae. Full crystallographic information is available from OCA.

Reference

Solution-state NMR investigations of triosephosphate isomerase active site loop motion: ligand release in relation to active site loop dynamics., Rozovsky S, Jogl G, Tong L, McDermott AE, J Mol Biol. 2001 Jun 29;310(1):271-80. PMID:11419952

Page seeded by OCA on Tue Jul 1 10:23:22 2008

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