Studies on the Stimulating Nature of Uncouplers on the Electron Transport in BBY Particles

BBY particles, which have kept the physicochemical property of PSII, were shown by transmission electron microscopy to possess no intact thylakoid membranes. The results of measuring 9-AA fluorescence quenching and millisecond Chl alpha delayed light emission proved that BBY particles were also unable to establish proton gradient across the membranes (deltapH) in light. Moreover, uncouplers gramicidin D and NH(4)Cl increased PSII electron transport in BBY particles only at low pH. This stimulation was more obvious around pH 6.0 than at other pH. The consistent stimulating value and pH-dependence indicated that the stimulating mechanisms of the two uncouplers are similar. From above, we infer that the uncouplers can bypass the proton transfer of localized pathway in BBY particles, stimulating the corresponding electron transport.