Conversion of allyl alcohol into acrolein by rat liver

1. Acrolein was detected in rat liver suspensions incubated in the presence of allyl alcohol and allyl formate. Acrolein was determined by condensation of the distilled aldehyde with semicarbazide, followed by spectrophotometric measurement of the semicarbazone at 257nm and identification by paper chromatography. 2. The transformation of allyl alcohol into acrolein occurred in the presence of NAD(+). Inhibitors of rat liver alcohol dehydrogenase inhibited the reaction. 3. It is suggested that the hepatotoxic actions of allyl alcohol and of allyl formate on rat liver are related to their conversion into acrolein.     

Urease production and DNA-homology in the species Bifidobacterium suis

Summary Urease production in the species Bifidobacterium suis was studied. The strains examined were strictly homogeneous in their DNA homology relationships. Most strains (74%) possess this enzyme. The presence of urease is therefore of value as additional diagnostic character of this species.     

A conformational study in solution of pro-somatostatin fragments by NMR and computational methods

The results of a conformational study by nuclear magnetic spectroscopy and computational methods on a series of point-mutated synthetic peptides, containing 14 amino acid residues and mimicking the region containing the Arg-Lys dibasic cleavage site of pro-somatostatin, have confirmed the possible role of a well defined secondary structure in the recognition phenomenon by processing enzymes. The importance of the residues located near the Arg-Lys dibasic site in the C-terminal region of the pro-hormone for the cleavage of the precursor into somatostatin-14 has been confirmed. The present structural analysis indicates the occurrence of two β-turns in the 4–7 and 11–14 regions, flanking the cleavage site, for all the peptides recognized as substrates by the processing enzyme. Interestingly, in the point-mutated analogue not processed by the enzyme and containing the replacement of proline by alanine in position 5 the first β-turn is displaced by one residue and involves the Ala⁵-Arg⁸ segment. This observation may explain the lack of recognition by the maturation enzyme. © 1998 European Peptide Society and John Wiley & Sons, Ltd.     

Generation and characterization of a human single-chain fragment variable (scFv) antibody against cytosine deaminase from Yeast

Background  

The ability of cytosine deaminase (CD) to convert the antifungal agent 5-fluorocytosine (5-FC) into one of the most potent and largely used anticancer compound such as 5-fluorouracil (5-FU) raised considerable interest in this enzyme to model gene or antibody – directed enzyme-prodrug therapy (GDEPT/ADEPT) aiming to improve the therapeutic ratio (benefit versus toxic side-effects) of cancer chemotherapy. The selection and characterization of a human monoclonal antibody in single chain fragment (scFv) format represents a powerful reagent to allow in in vitro and in vivo detection of CD expression in GDEPT/ADEPT studies.     

Multi-scale simulations provide supporting evidence for the hypothesis of intramolecular protein translocation in GroEL/GroES complexes

The biological function of chaperone complexes is to assist the folding of non-native proteins. The widely studied GroEL chaperonin is a double-barreled complex that can trap non-native proteins in one of its two barrels. The ATP-driven binding of a GroES cap then results in a major structural change of the chamber where the substrate is trapped and initiates a refolding attempt. The two barrels operate anti-synchronously. The central region between the two barrels contains a high concentration of disordered protein chains, the role of which was thus far unclear. In this work we report a combination of atomistic and coarse-grained simulations that probe the structure and dynamics of the equatorial region of the GroEL/GroES chaperonin complex. Surprisingly, our simulations show that the equatorial region provides a translocation channel that will block the passage of folded proteins but allows the passage of secondary units with the diameter of an alpha-helix. We compute the free-energy barrier that has to be overcome during translocation and find that it can easily be crossed under the influence of thermal fluctuations. Hence, strongly non-native proteins can be squeezed like toothpaste from one barrel to the next where they will refold. Proteins that are already fairly close to the native state will not translocate but can refold in the chamber where they were trapped. Several experimental results are compatible with this scenario, and in the case of the experiments of Martin and Hartl, intra chaperonin translocation could explain why under physiological crowding conditions the chaperonin does not release the substrate protein.     

Oxidosqualene cyclase from Saccharomyces cerevisiae,Trypanosoma cruzi,Pneumocystis carinii and Arabidopsis thaliana expressed in yeast: A model for the development of novel antiparasitic agents

A series of 25 compounds, some of which previously were described as inhibitors of human liver microsomal oxidosqualene cyclase (OSC), were tested as inhibitors of Saccharomyces cerevisiae, Trypanosoma cruzi, Pneumocystis carinii and Arabidopsis thaliana OSCs expressed in an OSC-defective strain of S. cerevisiae. The screening identified three derivatives particularly promising for the development of novel anti-Trypanosoma agents and eight derivatives for the development of novel anti-Pneumocystis agents.