Cytosol

Fig. 1.9.3. Composition and mechanism of a plant ABC transporter from the multidrug resistance associated protein (MRP) family. After the compound X is conjugated with glutathione by a glutathione-S-transferase, it can be transported by the MRP into the vacuole. N, N-terminus; C, C-terminus; TM (1,2) trans-membrane domains; NBF (1,2) nucleotide binding pockets; R putative regulatory domain. (After Rea et al. 1997)

ary acyl phosphate (perhaps with glutathione) is formed, indicated by the very strong inhibition by vanadate (formation of an acyl vanadate instead of the acyl phosphate). Remarkably, these transporters translocate glutathione conjugates, as well as GSSG (oxidised glutathione), but not reduced glutathione (GSH). So far, three such transporters which differ in substrate specificities have been described from Arabidopsis thaliana (AtMRP).

Phase I

Phase II

Phase I

Vacuole

0-(malonyl)-glucoside ch= ch —ch2oh ch= ch —ch2oh

Cell wall

Lignin conjugate

Cell wall

Lignin conjugate

Extracellular chemical

Transformation e.g. oxidation, reduction, hydrolysis

Vacuole

Intracellular chemical

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