1yfz

Novel IMP Binding in Feedback Inhibition of Hypoxanthine-Guanine Phosphoribosyltransferase from Thermoanaerobacter tengcongensis

spinqualitylabelsall models 1yfz, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1yfz is a 2 chain structure with sequence from Caldanaerobacter subterraneus subsp. tengcongensis MB4. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.2Å Ligands: ACT, IMP, MG Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q8R7L0_CALS4 Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed Crystal structures of Thermoanaerobacter tengcongensis hypoxanthine-guanine phosphoribosyltransferase (HGPRT) apoenzyme and the enzyme-inosine monophosphate (IMP) complex have been determined to 2.5A and 2.2A resolution, respectively. The active form of the enzyme was identified as a tetramer in solution and the K(i) value of IMP was measured to be 45 microM for alpha-D-phosphoribosyl-1-pyrophosphate (PRPP). Conformation of the flexible loop in T.tengcongensis HGPRT, which is involved in substrate PRPP binding, is different from that observed in phosphoribosyltransferases (PRTs). It contains a 3-10 helix, and a unique double serine repeat. This loop is ordered even in the apoenzyme and assumes a half-closed conformation. The primary magnesium ion is directly coordinated by side-chains of Glu101 and Asp102, and water molecules in the apoenzyme, suggesting a possible prerequisite role for substrate PRPP binding. Most interestingly, an alternative IMP binding mode is found in the structure of T.tengcongensis HGPRT-IMP complex. The 5'-phosphate of IMP occupies the PPi position usually seen in PRT-PRPP complexes. This new observation is consistent with the lower K(i) value of IMP and may suggest a mechanism involving multiple modes of interactions between IMP and T.tengcongensis HGPRT in product release and feedback inhibition. The structure of T.tengcongensis HGPRT is compared with those of mesophilic HPRTs, and several possible features contributing to its thermostability are elucidated. Overall, T.tengcongensis HGPRT appears to be more diverged from other PRTs. Alternative IMP binding in feedback inhibition of hypoxanthine-guanine phosphoribosyltransferase from Thermoanaerobacter tengcongensis.,Chen Q, Liang Y, Su X, Gu X, Zheng X, Luo M J Mol Biol. 2005 May 20;348(5):1199-210. Epub 2005 Apr 7. PMID:15854655 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Phosphoribosyltransferase 3D structures

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