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1z7g

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[[Image:1z7g.gif|left|200px]]
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{{STRUCTURE_1z7g| PDB=1z7g | SCENE= }}
{{STRUCTURE_1z7g| PDB=1z7g | SCENE= }}
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'''Free human HGPRT'''
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===Free human HGPRT===
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==Overview==
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Human hypoxanthine-guanine phosphoribosyltransferase (HGPRT) catalyses the synthesis of the purine nucleoside monophosphates, IMP and GMP, by the addition of a 6-oxopurine base, either hypoxanthine or guanine, to the 1-beta-position of 5-phospho-alpha-d-ribosyl-1-pyrophosphate (PRib-PP). The mechanism is sequential, with PRib-PP binding to the free enzyme prior to the base. After the covalent reaction, pyrophosphate is released followed by the nucleoside monophosphate. A number of snapshots of the structure of this enzyme along the reaction pathway have been captured. These include the structure in the presence of the inactive purine base analogue, 7-hydroxy [4,3-d] pyrazolo pyrimidine (HPP) and PRib-PP.Mg2+, and in complex with IMP or GMP. The third structure is that of the immucillinHP.Mg(2+).PP(i) complex, a transition-state analogue. Here, the first crystal structure of free human HGPRT is reported to 1.9A resolution, showing that significant conformational changes have to occur for the substrate(s) to bind and for catalysis to proceed. Included in these changes are relative movement of subunits within the tetramer, rotation and extension of an active-site alpha-helix (D137-D153), reorientation of key active-site residues K68, D137 and K165, and the rearrangement of three active-site loops (100-128, 165-173 and 186-196). Toxoplasma gondii HGXPRT is the only other 6-oxopurine phosphoribosyltransferase structure solved in the absence of ligands. Comparison of this structure with human HGPRT reveals significant differences in the two active sites, including the structure of the flexible loop containing K68 (human) or K79 (T.gondii).
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(as it appears on PubMed at http://www.pubmed.gov), where 15990111 is the PubMed ID number.
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{{ABSTRACT_PUBMED_15990111}}
==About this Structure==
==About this Structure==
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[[Category: Nucleotide binding]]
[[Category: Nucleotide binding]]
[[Category: Trans cis peptide bond isomerization]]
[[Category: Trans cis peptide bond isomerization]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 04:58:18 2008''

Revision as of 01:58, 29 July 2008

Image:1z7g.png

Template:STRUCTURE 1z7g

Free human HGPRT

Template:ABSTRACT PUBMED 15990111

About this Structure

1Z7G is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.

Reference

The crystal structure of free human hypoxanthine-guanine phosphoribosyltransferase reveals extensive conformational plasticity throughout the catalytic cycle., Keough DT, Brereton IM, de Jersey J, Guddat LW, J Mol Biol. 2005 Aug 5;351(1):170-81. PMID:15990111

Page seeded by OCA on Tue Jul 29 04:58:18 2008

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