The effect of chloroplast coupling factor removal on thylakoid membrane ion permeability

Removal of coupling factor protein (CF1) from spinach thylakoid membranes results in an enhancement of proton permeability but has no effect on chloride or potassium permeability. Anion permeability was measured by the rate of thylakoid packed volume changes. Potassium permeability was monitored by turbidity changes, packed thylakoid volume changes and ion flux studies using 86Rb+ as a tracer. 45Ca2+ was used to measure divalent cation fluxes. CF1-depleted chloroplasts had an unaltered rate of Ca2+ uptake, but the rate of Ca2+ efflux appeared to be increased. Calcium efflux rates could also be increased by the addition of a proton specific uncoupler, FCCP.