1pud
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(New page: 200px<br /><applet load="1pud" size="450" color="white" frame="true" align="right" spinBox="true" caption="1pud, resolution 1.85Å" /> '''TRNA-GUANINE TRANSGL...)
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Revision as of 22:00, 20 November 2007
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TRNA-GUANINE TRANSGLYCOSYLASE
Overview
tRNA-guanine transglycosylases (TGT) are enzymes involved in the, modification of the anticodon of tRNAs specific for Asn, Asp, His and Tyr, leading to the replacement of guanine-34 at the wobble position by the, hypermodified base queuine. In prokaryotes TGT catalyzes the exchange of, guanine-34 with the queuine (.)precursor 7-aminomethyl-7-deazaguanine, (preQ1). The crystal structure of TGT from Zymomonas mobilis was solved by, multiple isomorphous replacement and refined to a crystallographic, R-factor of 19% at 1.85 angstrom resolution. The structure consists of an, irregular (beta/alpha)8-barrel with a tightly attached C-terminal, zinc-containing subdomain. The packing of the subdomain against the barrel, is mediated by an alpha-helix, located close to the C-terminus, which, displaces the eighth helix of the barrel. The structure of TGT in complex, with preQ1 suggests a binding mode for tRNA where the phosphate backbone, interacts with the zinc subdomain and the U33G34U35 sequence is recognized, by the barrel. This model for tRNA binding is consistent with a base, exchange mechanism involving a covalent tRNA-enzyme intermediate. This, structure is the first example of a (beta/alpha)-barrel protein, interacting specifically with a nucleic acid.
About this Structure
1PUD is a Single protein structure of sequence from Zymomonas mobilis with ZN as ligand. Active as Queuine tRNA-ribosyltransferase, with EC number 2.4.2.29 Full crystallographic information is available from OCA.
Reference
Crystal structure of tRNA-guanine transglycosylase: RNA modification by base exchange., Romier C, Reuter K, Suck D, Ficner R, EMBO J. 1996 Jun 3;15(11):2850-7. PMID:8654383
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