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=MECHANISM=
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In the large mobile loop of the XGRT, there are several residues that are critical for substrate binding and catalysis<ref name="Vos"/>.
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==Recognition==
==Recognition==

Revision as of 02:30, 3 April 2011

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PDB ID 1a96

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1a96, resolution 2.00Å ()
Ligands: , , ,
Gene: GPT (Escherichia coli)
Activity: Xanthine phosphoribosyltransferase, with EC number 2.4.2.22
Resources: FirstGlance, OCA, RCSB, PDBsum
Coordinates: save as pdb, mmCIF, xml




XANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE

Contents

Introduction

Xanthine-guanine Phosphoribosyltansferase (XGPRT) is one of three purine phosphoribosyltransferases (PRTases) that are part of the purine salvage pathway in Escherichia coli[1]; the other two PRTases in the pathway are HPRT and APRT[1]

Structure

PRTase structures fall into two groups, type I and Type II[1]. XGTPase has a conserved sequence,, which is called the PRib-PP (5-phospho-a-D-ribosyl-1-pyrophosphate) binding site[1]. This binding site features two adjacent acidic residues, which are surrounded by hydrophobic residues[1]. There is a five-stranded b-sheet surrounded by three or four a-helices that creates a conserved structural core containing the PRib-PP binding site[1]. Another region of the sequence in XGTPase forms a lobe, which is involved in substrate recognition[1].

Function

XGRT is an enzyme that catalyzes the conversion of guanine, xanthine, and sometimes hypoxanthine, to GMP, XMP, and IMP [1].

Insert caption here

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MECHANISM

In the large mobile loop of the XGRT, there are several residues that are critical for substrate binding and catalysis[1].

Recognition

Catalysis

Magnesium and other divalent cations are necessary for catalysis[1].


References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Vos S, Parry RJ, Burns MR, de Jersey J, Martin JL. Structures of free and complexed forms of Escherichia coli xanthine-guanine phosphoribosyltransferase. J Mol Biol. 1998 Oct 2;282(4):875-89. PMID:9743633 doi:10.1006/jmbi.1998.2051
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