2d2k

Crystal Structure of a minimal, native (U39) all-RNA hairpin ribozyme

spinqualitylabelsall models 2d2k, resolution 2.65Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2d2k is a 4 chain structure. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: NCO, SO4 NonStd Res: A2M Related: 1x9c, 1x9k, 2d2l Resources: FirstGlance, OCA, RCSB, PDBsum Publication Abstract from PubMed The hairpin ribozyme is an RNA enzyme that performs site-specific phosphodiester bond cleavage between nucleotides A-1 and G+1 within its cognate substrate. Previous functional studies revealed that the minimal hairpin ribozyme exhibited "gain-of-function" cleavage properties resulting from U39C or U39 to propyl linker (C3) modifications. Furthermore, each "mutant" displayed different magnesium-dependence in its activity. To investigate the molecular basis for these gain-of-function variants, crystal structures of minimal, junctionless hairpin ribozymes were solved in native (U39), and mutant U39C and U39(C3) forms. The results revealed an overall molecular architecture comprising two docked internal loop domains folded into a wishbone shape, whose tertiary interface forms a sequestered active site. All three minimal hairpin ribozymes bound Co(NH(3))(6)(3+) at G21/A40, the E-loop/S-turn boundary. The native structure also showed that U37 of the S-turn adopts both sequestered and exposed conformations that differ by a maximum displacement of 13 A. In the sequestered form, the U37 base packs against G36, and its 2'-hydroxyl group forms a water mediated hydrogen bond to O4' of G+1. These interactions were not observed in previous four-way-junction hairpin ribozyme structures due to crystal contacts with the U1A splicing protein. Interestingly, the U39C and U39(C3) mutations shifted the equilibrium conformation of U37 into the sequestered form through formation of new hydrogen bonds in the S-turn, proximal to the essential nucleotide A38. A comparison of all three new structures has implications for the catalytically relevant conformation of the S-turn and suggests a rationale for the distinctive metal dependence of each mutant. Conformational heterogeneity at position U37 of an all-RNA hairpin ribozyme with implications for metal binding and the catalytic structure of the S-turn.,Alam S, Grum-Tokars V, Krucinska J, Kundracik ML, Wedekind JE Biochemistry. 2005 Nov 8;44(44):14396-408. PMID:16262240 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Ribozyme

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