1q2s
From Proteopedia
Chemical trapping and crystal structure of a catalytic tRNA guanine transglycosylase covalent intermediate
Structural highlights
FunctionTGT_ZYMMO Exchanges the guanine residue with 7-aminomethyl-7-deazaguanine in tRNAs with GU(N) anticodons (tRNA-Asp, -Asn, -His and -Tyr). After this exchange, a cyclopentendiol moiety is attached to the 7-aminomethyl group of 7-deazaguanine, resulting in the hypermodified nucleoside queuosine (Q) (7-(((4,5-cis-dihydroxy-2-cyclopenten-1-yl)amino)methyl)-7-deazaguanosine).[HAMAP-Rule:MF_00168] 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 PubMedProkaryotic tRNA guanine transglycosylase (TGT) catalyzes replacement of guanine (G) by 7-aminomethyl-7-deazaguanine (PreQ1) at the wobble position of four specific tRNAs. Addition of 9-deazaguanine (9dzG) to a reaction mixture of Zymomonas mobilis TGT and an RNA substrate allowed us to trap, purify and crystallize a chemically competent covalent intermediate of the TGT-catalyzed reaction. The crystal structure of the TGT-RNA-9dzG ternary complex at a resolution of 2.9 A reveals, unexpectedly, that RNA is tethered to TGT through the side chain of Asp280. Thus, Asp280, instead of the previously proposed Asp102, acts as the nucleophile for the reaction. The RNA substrate adopts an unusual conformation, with four out of seven nucleotides in the loop region flipped out. Interactions between TGT and RNA revealed by the structure provide the molecular basis of the RNA substrate requirements by TGT. Furthermore, reaction of PreQ1 with the crystallized covalent intermediate provides insight into the necessary structural changes required for the TGT-catalyzed reaction to occur. Chemical trapping and crystal structure of a catalytic tRNA guanine transglycosylase covalent intermediate.,Xie W, Liu X, Huang RH Nat Struct Biol. 2003 Oct;10(10):781-8. Epub 2003 Aug 31. PMID:12949492[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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