4gik
Crystal Structure of Pseudouridine Monophosphate Glycosidase/Linear R5P Adduct
Structural highlights
FunctionPSUG_ECOLI Catalyzes the reversible cleavage of pseudouridine 5'-phosphate (PsiMP) to ribose 5-phosphate and uracil. Functions biologically in the cleavage direction, as part of a pseudouridine degradation pathway.[HAMAP-Rule:MF_01876][1] [2] Publication Abstract from PubMedPseudouridine (Psi), the most abundant modification in RNA, is synthesized in situ using Psi synthase. Recently, a pathway for the degradation of Psi was described [Preumont, A., Snoussi, K., Stroobant, V., Collet, J. F., and Van Schaftingen, E. (2008) J. Biol. Chem. 283, 25238-25246]. In this pathway, Psi is first converted to Psi 5'-monophosphate (PsiMP) by Psi kinase and then PsiMP is degraded by PsiMP glycosidase to uracil and ribose 5-phosphate. PsiMP glycosidase is the first example of a mechanistically characterized enzyme that cleaves a C-C glycosidic bond. Here we report X-ray crystal structures of Escherichia coli PsiMP glycosidase and a complex of the K166A mutant with PsiMP. We also report the structures of a ring-opened ribose 5-phosphate adduct and a ring-opened ribose PsiMP adduct. These structures provide four snapshots along the reaction coordinate. The structural studies suggested that the reaction utilizes a Lys166 adduct during catalysis. Biochemical and mass spectrometry data further confirmed the existence of a lysine adduct. We used site-directed mutagenesis combined with kinetic analysis to identify roles for specific active site residues. Together, these data suggest that PsiMP glycosidase catalyzes the cleavage of the C-C glycosidic bond through a novel ribose ring-opening mechanism. Pseudouridine monophosphate glycosidase: a new glycosidase mechanism.,Huang S, Mahanta N, Begley TP, Ealick SE Biochemistry. 2012 Nov 13;51(45):9245-55. doi: 10.1021/bi3006829. Epub 2012 Oct, 30. PMID:23066817[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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