ABSTRACT
Sleeping sickness is a fatal disease caused by the protozoan parasite Trypanosoma brucei (Tb). Inosine-5'-monophosphate dehydrogenase (IMPDH) has been proposed as a potential drug target, since it maintains the balance between guanylate deoxynucleotide and ribonucleotide levels that is pivotal for the parasite. Here we report the structure of TbIMPDH at room temperature utilizing free-electron laser radiation on crystals grown in living insect cells. The 2.80 Å resolution structure reveals the presence of ATP and GMP at the canonical sites of the Bateman domains, the latter in a so far unknown coordination mode. Consistent with previously reported IMPDH complexes harboring guanosine nucleotides at the second canonical site, TbIMPDH forms a compact oligomer structure, supporting a nucleotide-controlled conformational switch that allosterically modulates the catalytic activity. The oligomeric TbIMPDH structure we present here reveals the potential of in cellulo crystallization to identify genuine allosteric co-factors from a natural reservoir of specific compounds.
Subject(s)
Coenzymes/chemistry , Crystallization , IMP Dehydrogenase/chemistry , Trypanosoma brucei brucei/enzymology , Amino Acid Sequence , Animals , Binding Sites , Catalytic Domain , Cloning, Molecular , Guanosine Monophosphate , Models, Molecular , Protein Conformation , Sf9 Cells , Trypanosoma brucei brucei/geneticsABSTRACT
A composite electrode containing graphite, paraffin, AgO and CuO is described for the determination of the electrochemical oxygen demand (EOD) of waste waters. The oxidation of dissolved organic compounds at the electrode is based on a heterogeneous chemical reaction of AgO/CuO with the organic constituents of the waste water. This chemical reaction can be followed by a solid state electrochemical oxidation of the formed Ag(2)O/Cu(2)O. The method has been tested with various organic compounds and applied to real samples of sewage water. The EOD values correlate well to BOD and COD values.
ABSTRACT
Fluoxetine, a selective serotonin reuptake inhibitor, is currently being evaluated as a potential treatment for cocaine abuse. This 4-week inpatient study evaluated the pharmacologic interaction between fluoxetine and cocaine in healthy adult male volunteers (N = 5) with histories of cocaine abuse. Oral capsules were administered daily containing either placebo (weeks 1 and 4) or fluoxetine in a series of ascending doses (10, 20, 30, and 40 mg) where each dose was given for three to four consecutive days. Cocaine challenge sessions were conducted twice weekly, once at each active dose level and twice during both the placebo and washout phases. Subjects received three ascending intravenous doses of cocaine (0, 20, and 40 mg) 1.5 hours apart and were monitored on physiologic and subjective measures. Cocaine alone increased heart rate, blood pressure, and pupillary diameter and increased subjective reports reflecting positive mood effects and drug liking. Fluoxetine (40 mg) significantly decreased subjective ratings of cocaine's positive mood effects on several visual analog measures. Fluoxetine also attenuated the mydriatic effect of cocaine. No adverse physiologic interactions between the two drugs were observed on cardiovascular measures. These data suggest that fluoxetine may be safely used in the presence of cocaine use and should be investigated further as a potential pharmacotherapy for cocaine abuse.
