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1l1r

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{{STRUCTURE_1l1r| PDB=1l1r | SCENE= }}
{{STRUCTURE_1l1r| PDB=1l1r | SCENE= }}
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'''Crystal Structure of APRTase from Giardia lamblia Complexed with 9-deazaadenine, Mg2+ and PRPP'''
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===Crystal Structure of APRTase from Giardia lamblia Complexed with 9-deazaadenine, Mg2+ and PRPP===
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==Overview==
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The adenine phosphoribosyltransferase (APRTase) from Giardia lamblia was co-crystallized with 9-deazaadenine and sulfate or with 9-deazaadenine and Mg-phosphoribosylpyrophosphate. The complexes were solved and refined to 1.85 and 1.95 A resolution. Giardia APRTase is a symmetric homodimer with the monomers built around Rossman fold cores, an element common to all known purine phosphoribosyltransferases. The catalytic sites are capped with a small hood domain that is unique to the APRTases. These structures reveal several features relevant to the catalytic function of APRTase: 1) a non-proline cis peptide bond (Glu(61)-Ser(62)) is required to form the pyrophosphate binding site in the APRTase.9dA.MgPRPP complex but is a trans peptide bond in the absence of pyrophosphate group, as observed in the APRTase.9dA.SO4 complex; 2) a catalytic site loop is closed and fully ordered in both complexes, with Glu(100) from the catalytic loop acting as the acid/base for protonation/deprotonation of N-7 of the adenine ring; 3) the pyrophosphoryl charge is neutralized by a single Mg2+ ion and Arg(63), in contrast to the hypoxanthine-guanine phosphoribosyltransferases, which use two Mg2+ ions; and 4) the nearest structural neighbors to APRTases are the orotate phosphoribosyltransferases, suggesting different paths of evolution for adenine relative to other purine PRTases. An overlap comparison of AMP and 9-deazaadenine plus Mg-PRPP at the catalytic sites of APRTases indicated that reaction coordinate motion involves a 2.1-A excursion of the ribosyl anomeric carbon, whereas the adenine ring and the 5-phosphoryl group remained fixed. G. lamblia APRTase therefore provides another example of nucleophilic displacement by electrophile migration.
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{{ABSTRACT_PUBMED_12171925}}
==About this Structure==
==About this Structure==
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[[Category: Giardia lamblia]]
[[Category: Giardia lamblia]]
[[Category: Purine metabolism]]
[[Category: Purine metabolism]]
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Revision as of 08:30, 2 July 2008

Image:1l1r.png

Template:STRUCTURE 1l1r

Crystal Structure of APRTase from Giardia lamblia Complexed with 9-deazaadenine, Mg2+ and PRPP

Template:ABSTRACT PUBMED 12171925

About this Structure

1L1R is a Single protein structure of sequence from Giardia intestinalis. Full crystallographic information is available from OCA.

Reference

Closed site complexes of adenine phosphoribosyltransferase from Giardia lamblia reveal a mechanism of ribosyl migration., Shi W, Sarver AE, Wang CC, Tanaka KS, Almo SC, Schramm VL, J Biol Chem. 2002 Oct 18;277(42):39981-8. Epub 2002 Aug 8. PMID:12171925

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