Pseudouridine monophosphate glycosidase: a new glycosidase mechanism.
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ABSTRACT: Pseudouridine (?), the most abundant modification in RNA, is synthesized in situ using ? synthase. Recently, a pathway for the degradation of ? 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, ? is first converted to ? 5'-monophosphate (?MP) by ? kinase and then ?MP is degraded by ?MP glycosidase to uracil and ribose 5-phosphate. ?MP 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 ?MP glycosidase and a complex of the K166A mutant with ?MP. We also report the structures of a ring-opened ribose 5-phosphate adduct and a ring-opened ribose ?MP 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 ?MP glycosidase catalyzes the cleavage of the C-C glycosidic bond through a novel ribose ring-opening mechanism.
SUBMITTER: Huang S
PROVIDER: S-EPMC3526674 | biostudies-literature | 2012 Nov
REPOSITORIES: biostudies-literature
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