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Publication Abstract from PubMed

Uridylate kinase (UMPK; EC 2.7.4.22) transfers the gamma-phosphate of ATP to UMP, forming UDP. It is allosterically regulated by GTP. Structures of Helicobacter pylori UMPK (HpUMPK) complexed with GTP (HpUMPK-GTP) and with UDP (HpUMPK-UDP) were determined at 1.8 and 2.5 A resolution, respectively. As expected, HpUMPK-GTP forms a hexamer with six GTP molecules at its centre. Interactions between HpUMPK and GTP are made by the beta3 strand of the sheet, loop beta3alpha4 and the alpha4 helix. In HpUMPK-UDP, the hexameric symmetry typical of UMPKs is absent. Only four of the HpUMPK molecules bind UDP; the other two HpUMPK molecules are in the UDP-free state. The asymmetric hexamer of HpUMPK-UDP, which has an exposed dimer interface, may assist in UDP release. Furthermore, the flexibility of the alpha2 helix, which interacts with UDP, is found to increase when UDP is absent in HpUMPK-UDP. In HpUMPK-GTP, the alpha2 helix is too flexible to be observed. This suggests that GTP binding may affect the conformation of the alpha2 helix, thereby promoting UDP release.

Structures of Helicobacter pylori uridylate kinase: insight into release of the product UDP.,Chu CH, Liu MH, Chen PC, Lin MH, Li YC, Hsiao CD, Sun YJ Acta Crystallogr D Biol Crystallogr. 2012 Jul;68(Pt 7):773-83. Epub 2012 Jun 15. PMID:22751662^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.