The Effect of Dinactin on Potassium Transport in Chloroplasts

Abstract

Dinactin is a member of the group of macrotetralide antibiotics.These are lipophilic compounds which show a strong biological activity and which are produced by certain strains of actinomycetes. In mitochondria macrotetralides seem to act in a similar manner to valinomycin. In chloroplasts only few results are available at this time. KARLISH et al. (1969) postulated that a mixture of nonactin and monactin increased the permeability of the chloroplast membrane for cations as valinomycin. On the other hand these compounds produced uncoupling effects when added in the presence of FCCP or DNP. Later (BACHOFEN & SPECHT-JÜRGENSEN 1970) it was shown that the rates of several chloroplast reactions, the Hill-react ion, cyclic phosphorylation and proton transport, were altered by dinactin depending on the relation of K⁺ to Na⁺ in the medium. Since dinactin increases specifically the permeability for K⁺ in artificial (MUELLER & RUDIN I967) and natural membranes (KARLISH et al. 1969), the effects of the antibiotic on chloroplast reactions may be caused by this permeability change. Therefore, a direct investigation of the action of dinactin on K⁺ translocation snd the concomitant volume changes was undertaken.