Abstract
The effect of diethyl pyrocarbonate (DEPC) on the photosynthetic electron transport was investigated in isolated spinach thylakoids by partial electron transport rate and thermolumi- nescence measurements. Incubation of thylakoids at pH 6.5 with 5 mм DEPC for 15 min resulted in a considerable inhibition of electron transport from water to dichlorophenolindo- phenol. The inhibition was only partially releaved by addition of the donor, diphenylcarbazide indicating the effect of DEPC both on the donor and acceptor sides of PS II. In the thermoluminescence glow curve DEPC-treatment abolished the B band (S2QB - radiative charge recombination) at 30 °C with a concomitant appearance of the Q band (S2QA - charge recombination) at 10 °C. This suggests that in isolated thylakoids possessing an active water-splitting system DEPC affects the electron transfer from QA to QB but does not inhibit the electron transport from manganese to QA during the S,→S2 transition of the water-splitting system. At the acceptor side of PS II the targets of DEPC are probably the histidines which are coordinated to the non-heme iron. Illumination of thylakoids at -80 °C following DEPC addition after two preflashes at 5 °C resulted in the replacement of the A(AT) thermoluminescence band at -30 °C with a band appearing at -15 °C. This observation can be explained by the effect of DEPC on a donor side histidine component participating in the generation of the A(AT) band. Consequently, in the interpretation of results obtained by DEPC treatment of PS II, both the donor and acceptor side effects of DEPC should be considered.
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call