3kgd
From Proteopedia
Crystal structure of E. coli RNA 3' cyclase
Structural highlights
FunctionRTCA_ECOLI Catalyzes the conversion of 3'-phosphate to a 2',3'-cyclic phosphodiester at the end of RNA. The mechanism of action of the enzyme occurs in 3 steps: (A) adenylation of the enzyme by ATP; (B) transfer of adenylate to an RNA-N3'P to produce RNA-N3'PP5'A; (C) and attack of the adjacent 2'-hydroxyl on the 3'-phosphorus in the diester linkage to produce the cyclic end product. The biological role of this enzyme is unknown but it is likely to function in some aspects of cellular RNA processing.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedRNA 3'-phosphate cyclase (RtcA) synthesizes RNA 2',3' cyclic phosphate ends via three steps: reaction with ATP to form a covalent RtcA-AMP intermediate; transfer of adenylate to an RNA 3'-phosphate to form RNA(3')pp(5')A; and attack of the vicinal O2' on the 3'-phosphorus to form a 2',3' cyclic phosphate. Here we report the 1.7 A crystal structure of the RtcA-AMP intermediate, which reveals the mechanism of nucleotidyl transfer. Adenylate is linked via a phosphoamide bond to the His309 Nepsilon atom. A network of hydrogen bonds to the ribose O2' and O3' accounts for the stringent ribonucleotide preference. Adenine is sandwiched in a hydrophobic pocket between Tyr284 and Pro131 and the preference for adenine is enforced by Phe135, which packs against the purine C2 edge. Two sulfates bound near the adenylate plausibly mimic the 3'-terminal and penultimate phosphates of RNA. The structure illuminates how the four alpha2/beta4 domains contribute to substrate binding and catalysis. Structure of the RNA 3'-phosphate cyclase-adenylate intermediate illuminates nucleotide specificity and covalent nucleotidyl transfer.,Tanaka N, Smith P, Shuman S Structure. 2010 Mar 14;18(4):449-57. PMID:20399182[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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