5d6s | pdb_00005d6s

Structure of epoxyqueuosine reductase from Streptococcus thermophilus.

spinqualitylabelsall models 5d6s, resolution 2.65Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 5d6s is a 5 chain structure with sequence from Streptococcus thermophilus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.65Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function A0A0R4I997_STRTR Publication Abstract from PubMed Queuosine (Q) is a hypermodified RNA base that replaces guanine in the wobble positions of 5prime-GUN-3prime tRNA molecules. Q is exclusively made by bacteria, and the corresponding queuine base is a micronutrient salvaged by eukaryotic species. The final step in Q biosynthesis is the reduction of the epoxide precursor, epoxyqueuosine, to yield the Q cyclopentene ring. The epoxyqueuosine reductase responsible, QueG, shares distant homology with the cobalamin-dependent reductive dehalogenase (RdhA), however the role played by cobalamin in QueG catalysis has remained elusive. We report the solution and structural characterization of Streptococcus thermophilus QueG, revealing the enzyme harbours a redox chain consisting of two [4Fe-4S] clusters and a cob(II)alamin in the base-off form, similar to RdhAs. In contrast to the shared redox chain architecture, the QueG active site shares little homology with RdhA, with the notable exception of a conserved Tyr that is proposed to function as a proton donor during reductive dehalogenation. Docking of an epoxyqueuosine substrate suggests the QueG active site places the substrate cyclopentane moiety in close proximity of the cobalt. Both the Tyr and a conserved Asp are implicated as proton donors to the epoxide leaving group. This suggests that, in contrast to the unusual carbon-halogen bond chemistry catalyzed by RdhAs, QueG acts via Co-C bond formation. Our study establishes the common features of Class III cobalamin-dependent enzymes, and reveal an unexpected diversity in the reductive chemistry catalyzed by these enzymes. Epoxyqueuosine Reductase Structure suggests a Mechanism for Cobalamin-dependent tRNA Modification.,Payne KA, Fisher K, Sjuts H, Dunstan MS, Bellina B, Johannissen L, Barran P, Hay S, Rigby SE, Leys D J Biol Chem. 2015 Sep 16. pii: jbc.M115.685693. PMID:26378237 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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