Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01350 (gastrin)
 9,683 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Escherichia coli tRNA-guanine transglycosylase is an enzyme which catalyzes replacement of guanine (G34) of tRNA(Asp), tRNA(Asn), tRNA(His) and tRNA(Tyr) by free guanine or free preQ1 base by a base exchange reaction in the biosynthesis of queuosine (Q) (Okada, N., and Nishimura, S. (1979) J. Biol. Chem. 254, 3061-3066). The gene encoding for this enzyme was amplified from the E. coli genome by polymerase chain reaction and inserted into an overexpression vector, pJLA503. The enzyme was overexpressed by heat induction in E. coli transformed by this recombinant plasmid and purified to homogeneity by two column chromatographies. The sequence requirement in tRNA for recognition by this enzyme was investigated using minihelices corresponding to the anti-codon arm of E. coli tRNA(His). Two uridine residues (U33, U35) were found to be prerequisite for such recognition by this enzyme. Position 32 required pyrimidines, because the enzyme activity toward the minihelices was markedly reduced or entirely lost when this residue was replaced by purines or was deleted. Adenosine at position 37 and the G30-C40 base pair were not essential despite their conservation. Our results suggest that the enzyme recognizes the U33-G34-U35 sequence in the anti-codon loop and not the tertiary structure of tRNA itself.
 ...
PMID:A UGU sequence in the anticodon loop is a minimum requirement for recognition by Escherichia coli tRNA-guanine transglycosylase. 752 9

A series of 5-substituted 2-aminopyrrolo[2,3-d]pyrimidin-4(3H)-ones have been synthesized in order to study the substrate specificity of the tRNA-guanine transglycosylase (TGT) from Escherichia coli. A number of these compounds were initially examined as inhibitors of radiolabeled guanine incorporation into tRNA catalyzed by TGT [Hoops, G. C., Garcia, G. A., & Townsend, L. B. (1992) 204th National Meeting of the American Chemical Society, Washington, DC, August 23-28, 1992, Division of Medicinal Chemistry, Abstract 113]. The kinetic parameters of these analogues as substrates in the TGT reaction have been determined by monitoring the loss of radiolabeled guanine from 8-[14C]G34-tRNA. This study reveals that the tRNA-guanine transglycosylase from E. coli will tolerate a wide variety of substituents at the 5-position. The role of the 5-substituent appears to be entirely in binding/recognition with no apparent effects upon catalysis. A correlation between N7 pKa and Vmax suggests the deprotonation of N7 during the reaction, which must occur prior to subsequent glycosidic bond formation, appears to be partially rate-determining for the natural substrate. Comparison of the Kis of 7-methyl-substituted competitive inhibitors to the Kms of their corresponding substrates suggests that some substrates (including preQ1) are kinetically "sticky" (i.e., Km is equivalent to Kd) and other substrates have Kms that reflect catalytic rates as well as binding.
 ...
PMID:tRNA-guanine transglycosylase from Escherichia coli: structure-activity studies investigating the role of the aminomethyl substituent of the heterocyclic substrate PreQ1. 757 54

Eubacterial tRNA-guanine transglycosylase (TGT) is involved in the hyper-modification of cognate tRNAs leading to the exchange of G34 at the wobble position in the anticodon loop by preQ1 (2-amino-5-(aminomethyl)pyrrolo[2,3-d]pyrimidin-4(3H)-one) as part of the biosynthesis of queuine (Q). Mutation of the tgt gene in Shigella flexneri results in a significant loss of pathogenicity of the bacterium, revealing TGT as a new target for the design of potent drugs against Shigellosis. The X-ray structure of Zymomonas mobilis TGT in complex with preQ1 was used to search for new putative inhibitors with the computer program LUDI. An initial screen of the Available Chemical Directory, a database compiled from commercially available compounds, suggested several hits. Of these, 4-aminophthalhydrazide (APH) showed an inhibition constant in the low micromolar range. The 1.95 A crystal structure of APH in complex with Z. mobilis TGT served as a starting point for further modification of this initial lead.
 ...
PMID:A new target for shigellosis: rational design and crystallographic studies of inhibitors of tRNA-guanine transglycosylase. 1117 5

Eubacterial tRNA-guanine transglycosylase (TGT) is involved in the hypermodification of cognate tRNAs, leading to the exchange of G34 by preQ1 at the wobble position in the anticodon loop. Mutation of the tgt gene in Shigella flexneri results in a significant loss of pathogenicity of the bacterium due to inefficient translation of a virulence protein mRNA. Herein, we describe the discovery of a ligand with an unexpected binding mode. On the basis of this binding mode, three slightly deviating pharmacophore hypotheses have been derived. Virtual screening based on this composite pharmacophore model retrieved a set of potential TGT inhibitors belonging to several compound classes. All nine tested inhibitors being representatives of these classes showed activity in the micromolar range, two of them even in the submicromolar range.
 ...
PMID:Virtual screening for submicromolar leads of tRNA-guanine transglycosylase based on a new unexpected binding mode detected by crystal structure analysis. 1264 24