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1p50

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{{STRUCTURE_1p50| PDB=1p50 | SCENE= }}
{{STRUCTURE_1p50| PDB=1p50 | SCENE= }}
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'''Transition state structure of an Arginine Kinase mutant'''
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===Transition state structure of an Arginine Kinase mutant===
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==Overview==
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Arginine kinase is a member of the phosphagen kinase family that includes creatine kinase and likely shares a common reaction mechanism in catalyzing the buffering of cellular ATP energy levels. Abstraction of a proton from the substrate guanidinium by a catalytic base has long been thought to be an early mechanistic step. The structure of arginine kinase as a transition state analog complex (Zhou, G., Somasundaram, T., Blanc, E., Parthasarathy, G., Ellington, W. R., and Chapman, M. S. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 8449-8454) showed that Glu-225 and Glu-314 were the only potential catalytic residues contacting the phosphorylated nitrogen. In the present study, these residues were changed to Asp, Gln, and Val or Ala in several single and multisite mutant enzymes. These mutations had little impact on the substrate binding constants. The effect upon activity varied with reductions in kcat between 3000-fold and less than 2-fold. The retention of significant activity in some mutants contrasts with published studies of homologues and suggests that acid-base catalysis by these residues may enhance the rate but is not absolutely essential. Crystal structures of mutant enzymes E314D at 1.9 A and E225Q at 2.8 A resolution showed that the precise alignment of substrates is subtly distorted. Thus, pre-ordering of substrates might be just as important as acid-base chemistry, electrostatics, or other potential effects in the modest impact of these residues upon catalysis.
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(as it appears on PubMed at http://www.pubmed.gov), where 12732621 is the PubMed ID number.
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{{ABSTRACT_PUBMED_12732621}}
==About this Structure==
==About this Structure==
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[[Category: Phosphagen kinase]]
[[Category: Phosphagen kinase]]
[[Category: Transition state]]
[[Category: Transition state]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 04:41:44 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 23:42:49 2008''

Revision as of 20:42, 28 July 2008

Image:1p50.png

Template:STRUCTURE 1p50

Transition state structure of an Arginine Kinase mutant

Template:ABSTRACT PUBMED 12732621

About this Structure

1P50 is a Single protein structure of sequence from Limulus polyphemus. Full crystallographic information is available from OCA.

Reference

The putative catalytic bases have, at most, an accessory role in the mechanism of arginine kinase., Pruett PS, Azzi A, Clark SA, Yousef MS, Gattis JL, Somasundaram T, Ellington WR, Chapman MS, J Biol Chem. 2003 Jul 18;278(29):26952-7. Epub 2003 May 5. PMID:12732621

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