Figure 3.

The light-dependent ⁴⁵Ca²⁺ transport reaction is sensitive to nigericin. Reactions were initiated by adding ⁴⁵Ca²⁺ (1.5 μm final concentration) to thylakoid membranes suspended in import buffer in the light. Nigericin was added from an ethanolic stock to the concentration indicated. Potassium, approximately 25 mm, was present in the reaction as the counterion to the Tricine buffer. An equal volume of ethanol (1 μL per 60-μL reaction) was added to all reactions. Reactions were terminated after 15 min. Chl, Chlorophyll.