Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: DrugBank:EXPT01586 (G418)
 2,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Kinetoplastids are unicellular eukaryotes that include important parasites of man, such as trypanosomes and leishmanias. The study of these organisms received a recent boost from the development of transient transformation allowing the short-term expression of genes reintroduced into parasites like Trypanosoma brucei, the causative agent of African trypanosomiasis. We have obtained long-term stable transformants of T. brucei that have acquired the ability to grow in medium containing the drug G418, following the targeted insertion of the bacterial gene for neomycin phosphotransferase (neo(r) gene) into the trypanosome tubulin cluster. Plasmids in which part of the T. brucei tubulin gene cluster has been replaced by the neo(r) gene were used. Targeting efficiency was higher with a linearized than with a circular construct, and with 5 kilobases of tubulin gene cluster than with 0.9 kilobases. With these neo(r) constructs homologous recombination seems to be the preferred route for insertion of exogenous DNA into the trypanosome genome, allowing gene targeting without counter-selection.
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PMID:Targeted insertion of the neomycin phosphotransferase gene into the tubulin gene cluster of Trypanosoma brucei. 223 72

Ornithine decarboxylase (ODC) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the rate-determining step in the biosynthesis of polyamines. ODC is a proven drug target to treat African sleeping sickness. The x-ray crystal structure of Trypanosoma brucei ODC in complex with d-ornithine (d-Orn), a substrate analog, and G418 (Geneticin), a weak non-competitive inhibitor, was determined to 2.5-A resolution. d-Orn forms a Schiff base with PLP, and the side chain is in a similar position to that observed for putrescine and alpha-difluoromethylornithine in previous T. brucei ODC structures. The d-Orn carboxylate is positioned on the solvent-exposed side of the active site (si face of PLP), and Gly-199, Gly-362, and His-197 are the only residues within 4.2 A of this moiety. This structure confirms predictions that the carboxylate of d-Orn binds on the si face of PLP, and it supports a model in which the carboxyl group of the substrate l-Orn would be buried on the re face of the cofactor in a pocket that includes Phe-397, Tyr-389, Lys-69 (methylene carbons), and Asp-361. Electron density for G418 was observed at the boundary between the two domains within each ODC monomer. A ten-amino acid loop region (392-401) near the 2-fold axis of the dimer interface, which contributes several residues that form the active site, is disordered in this structure. The disordering of residues in the active site provides a potential mechanism for inhibition by G418 and suggests that allosteric inhibition from this site is feasible.
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PMID:X-ray structure determination of Trypanosoma brucei ornithine decarboxylase bound to D-ornithine and to G418: insights into substrate binding and ODC conformational flexibility. 1267 97