Flow-force relationship in lettuce thylakoids. 1. Strict control of electron flow by internal pH

The regulation by the proton gradient of the electron flow from water to ferricyanide was investigated in thylakoids extracted from lettuce leaves. When the transmembrane proton current was varied by an uncoupler or by the ATP synthase activity, a unique relationship was found between the rate of fe...

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Bibliographic Details
Published in:Biochemistry (Easton) 1993-09, Vol.32 (38)
Main Authors: Sigalat, C, Haraux, F, Kouchkovsky, Y. de
Format: Article
Language:English
Subjects:
ACTIVIDAD ENZIMATICA
ACTIVITE ENZYMATIQUE
ADENOSINA TRIFOSFATASA
ADENOSINE TRIPHOSPHATASE
ANION
ANIONES
CATION
CATIONES
FOTOSISTEMAS
HIDROGENO
HYDROGENE
ION
IONES
LACTUCA SATIVA
OXIRREDUCION
OXYDOREDUCTION
PHOTOSYSTEME
PLASTE
PLASTIDIOS
REDUCCION
REDUCTION
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Summary:The regulation by the proton gradient of the electron flow from water to ferricyanide was investigated in thylakoids extracted from lettuce leaves. When the transmembrane proton current was varied by an uncoupler or by the ATP synthase activity, a unique relationship was found between the rate of ferricyanide reduction and the proton gradient, restricted here to its pH component. This behavior was conserved in CF1-depleted thylakoids where the passive proton flow was varied by the concentration of an F(0) inhibitor or by the concentration of an uncoupler after 100% inhibition of F(0). This shows that under our experimental conditions no direct proton transfer exists in steady state between the site of regulation of the redox chain and the ATPase. Studies at two different pH's indicate that the internal pH, and not the transmembrane pH difference, controls the electron transfer between PS2 and PS1. Modeling the data suggests that a single deprotonation step is kinetically limiting
ISSN:0006-2960
1520-4995