Uncoupling of the recombination and topoisomerase activities of the gamma delta resolvase by a mutation at the crossover point

In several well-characterized site-specific recombination systems it has been shown that, for efficient recombination, the two recombining sites must have identical DNA sequences across the region between the staggered points of exchange. The precise DNA sequence of this overlap region, however, appears to be of little importance (with the exception of one position in the loxP site of bacteriophage P1 (ref. 6]. In this report we characterize a mutant recombination site for the site-specific recombination enzyme gamma delta resolvase (encoded by the gamma delta transposon), in which the dinucleotide at the crossover point is changed from AT to CT. Our results indicate that identity of the two overlap regions is not sufficient for recombination. Although resolvase binds normally to the mutant site and induces the structural deformation characteristic of the wild-type recombination site, catalysis at the crossover point (cutting and rejoining of DNA strands) is effectively limited to just one of the two strands, allowing resolvase to act as a topoisomerase but not as a recombinational enzyme.     

Some factors modifying the action of chlorpromazine upon the O2 uptake of brain homogenatesin vitro

Zusammenfassung Largactil vermindert auch in niedrigen Konzentrationen (10⁻⁶ g/ml der Krebs-Ringer-L?sung mit 0,2% Glukose) den Sauerstoffverbrauch von Gehirnhomogenaten weisser Ratten signifikant. Diese depressive Wirkung von Largactil tritt nicht ein, wenn die Krebs-Ringer-L?sung ohne Glukose oder ein kalziumfreies Medium zu den manometrischen Messungen gebraucht werden. Weiterhin hat Largactil eine antagonistische Wirkung gegen 2,4-Dinitrophenol in bezug auf die O₂-Aufnahme von Gehirngewebe.