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Tricolorin A, a potent natural uncoupler and inhibitor of photosystem II acceptor side of spinach chloroplasts
Author(s) -
Achnine Lahoucine,
PeredaMiranda Rogelio,
IglesiasPrieto Roberto,
MorenoSánchez Rafael,
LotinaHennsen Blas
Publication year - 1999
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1999.106215.x
Subject(s) - photophosphorylation , plastoquinone , submitochondrial particle , electron transport chain , photosystem ii , chloroplast , photosystem i , spinach , biochemistry , chemistry , dcmu , nigericin , stereochemistry , biology , thylakoid , photosynthesis , mitochondrion , membrane , gene
Tricolorin A, (11 S )‐11‐hydroxyhexadecanoic acid 11‐ O ‐ α ‐ l ‐ rhamnopyranosyl‐(1?3)‐ O ‐ α ‐ l ‐{2‐ O ‐(2 S ‐methylbutanoyl)‐4‐ O ‐(2 S ‐methylbutanoyl)}‐rhamnopyranosil‐(1?2)‐ O ‐ β ‐ d ‐glucopyranosil‐(1?2)‐ β ‐fucopyranoside‐(1,3′′‐lactone), the major phytogrowth inhibitor isolated from Ipomoea tricolor Cav. (Convolvulaceae) was found to be a potent uncoupler (U 50 =0.33 μ M ) of photophosphorylation in spinach chloroplasts. Tricolorin A inhibited H + ‐uptake and adenosine 5′‐triphosphate (ATP) synthesis, and stimulated basal and phosphorylating electron flows. Using a combination of two well‐known fluorescent ΔpH probes, 9‐aminoacridine and 9‐amino‐6‐chloro‐2‐methoxyacridine, the uncoupling behavior of tricolorin A was also demonstrated for submitochondrial particles. Polarographic data showed that high concentrations (20 μ M ) of tricolorin A inhibited photosystem II (PSII) electron flow at the level of plastoquinone B (Q B ). Chlorophyll (Chl) a fluorescence analysis showed that tricolorin A induced accumulation of Q A − and strongly decreased the electron transport capacity, suggesting that the target of this molecule was located at the Q B level. The macrocyclic lactone‐type structure of this allelopathic agent proved to be an important structural requirement for uncoupling activity since its hydrolysis caused loss of the inhibitory potential.