Zinc irons selectively inhibit steps associated with binding and release of NADP(H) during turnover of proton-translocating transhydrogenase
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Colleges, School and Institutes
Transhydrogenase couples the redox reaction between NAD(H) and NADP(H) to proton translocation across a membrane. In membrane vesicles from Escherichia coli and Rhodospirillum rubrum, the transhydrogenase reaction (measured in the direction driving inward proton translocation) was inhibited by Zn(2+) and Cd(2+). However, depending on pH, the metal ions either had no effect on, or stimulated, "cyclic" transhydrogenation. They must, therefore, interfere specifically with steps involving binding/release of NADP(+)/NADPH: the steps thought to be associated with proton translocation. It is suggested that Zn(2+) and Cd(2+) bind in the proton-transfer pathway and block inter-conversion of states responsible for changing NADP(+)/NADPH binding energy.
|Number of pages||5|
|Publication status||Published - 23 May 2005|
- membrane proteins, zinc ions, hydride transfer, nicotinamide nucleotides, proton translocation, transhydrogenase