1rtz: Difference between revisions

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[[Image:1rtz.jpg|left|200px]]
{{Seed}}
[[Image:1rtz.png|left|200px]]


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{{STRUCTURE_1rtz|  PDB=1rtz  |  SCENE=  }}  
{{STRUCTURE_1rtz|  PDB=1rtz  |  SCENE=  }}  


'''CRYSTAL STRUCTURE OF E.COLI APO-HPPK(V83G/DEL84-89) AT 1.33 ANGSTROM RESOLUTION'''
===CRYSTAL STRUCTURE OF E.COLI APO-HPPK(V83G/DEL84-89) AT 1.33 ANGSTROM RESOLUTION===




==Overview==
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6-Hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) catalyzes the transfer of pyrophosphoryl group from ATP to 6-hydroxymethyl-7,8-dihydropterin (HP) following an ordered bi-bi mechanism with ATP as the first substrate. The rate-limiting step of the reaction is product release, and the complete active center is assembled and sealed only upon the binding of both ATP and HP. The assembly of the active center involves large conformational changes in three catalytic loops, among which loop 3 undergoes the most dramatic and unusual changes. To investigate the roles of loop 3 in catalysis, we have made a deletion mutant, which has been investigated by biochemical and X-ray crystallographic analysis. The biochemical data showed that the deletion mutation does not have significant effects on the dissociation constants or the rate constants for the binding of the first substrate MgATP or its analogues. The dissociation constant of HP for the mutant increases by a factor of approximately 100, which is due to a large increase in the dissociation rate constant. The deletion mutation causes a shift of the rate-limiting step in the reaction and a decrease in the rate constant for the chemical step by a factor of approximately 1.1 x 10(5). The crystal structures revealed that the deletion mutation does not affect protein folding, but the catalytic center of the mutant is not fully assembled even upon the formation of the ternary complex and is not properly sealed. The results together suggest that loop 3 is dispensable for the folding of the protein and the binding of the first substrate MgATP, but is required for the assembling and sealing of the active center. The loop plays an important role in the stabilization of the ternary complex and is critical for catalysis.
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{{ABSTRACT_PUBMED_14769023}}


==About this Structure==
==About this Structure==
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==Reference==
==Reference==
Essential roles of a dynamic loop in the catalysis of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase., Blaszczyk J, Li Y, Wu Y, Shi G, Ji X, Yan H, Biochemistry. 2004 Feb 17;43(6):1469-77. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/14769023 14769023]
Essential roles of a dynamic loop in the catalysis of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase., Blaszczyk J, Li Y, Wu Y, Shi G, Ji X, Yan H, Biochemistry. 2004 Feb 17;43(6):1469-77. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/14769023 14769023]
Catalytic center assembly of HPPK as revealed by the crystal structure of a ternary complex at 1.25 A resolution., Blaszczyk J, Shi G, Yan H, Ji X, Structure. 2000 Oct 15;8(10):1049-58. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/11080626 11080626]
[[Category: 2-amino-4-hydroxy-6-hydroxymethyldihydropteridine diphosphokinase]]
[[Category: 2-amino-4-hydroxy-6-hydroxymethyldihydropteridine diphosphokinase]]
[[Category: Escherichia coli]]
[[Category: Escherichia coli]]
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[[Category: Pyrophosphoryl transfer]]
[[Category: Pyrophosphoryl transfer]]
[[Category: X-ray crystallography]]
[[Category: X-ray crystallography]]
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Revision as of 09:20, 28 July 2008

File:1rtz.png

Template:STRUCTURE 1rtz

CRYSTAL STRUCTURE OF E.COLI APO-HPPK(V83G/DEL84-89) AT 1.33 ANGSTROM RESOLUTION

Template:ABSTRACT PUBMED 14769023

About this Structure

1RTZ is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

Essential roles of a dynamic loop in the catalysis of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase., Blaszczyk J, Li Y, Wu Y, Shi G, Ji X, Yan H, Biochemistry. 2004 Feb 17;43(6):1469-77. PMID:14769023

Catalytic center assembly of HPPK as revealed by the crystal structure of a ternary complex at 1.25 A resolution., Blaszczyk J, Shi G, Yan H, Ji X, Structure. 2000 Oct 15;8(10):1049-58. PMID:11080626

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