A rapid burst preceding the steady-state rate of H+-transhydrogenase during illumination of chromatophores of Rhodobacter capsulatus. Implications for the mechanism of interaction between protonmotive force and enzyme

Tracy Palmer, J. Baz Jackson

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    Abstract

    At the onset of illumination of chromatophores there was a burst (t1/2 approx. 5 ms) in the rate of the H+-transhydrogenase reaction before establishment of the steady-state rate. The burst was suppressed at high pH with a pK(a) of approx. 8.5. The burst and the steady-state rate were inhibited by either (i) a combination of myxothiazol and carbonylcyanide-p-trifluoromethoxyphenylhydrazone, or (ii) NAD+, or (iii) dicyclohexylcarbodiimide. The results support a model in which substrate binding to H+-transhydrogenase is relatively fast. A subsequent slow step is accelerated by the protonmotive force and a third step, possibly product release, is rate-limiting in steady-state turnover during illumination.

    Original languageEnglish
    Pages (from-to)45-48
    Number of pages4
    JournalFEBS Letters
    Volume277
    Issue number1-2
    DOIs
    Publication statusPublished - 17 Dec 1990

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