1. 1. A simple kinetic analysis of light-induced proton uptake into chloroplasts is presented. It is derived from a model of the reaction in which the incoming proton is obligatorily bound by an intra-chloroplast component, and allows quantitative analysis of the effect into parameters of light and dark rate constants and the availability of the chloroplast component.
2. 2. The effect of the following agents on the derived parameters has been measured: electron and energy transfer inhibitors, uncouplers, NaCl concentration, light intensity and pH.
3. 3. A maximal ratio of 4 protons taken up per electron transported has been observed, using ferricyanide as an electron acceptor.
4. 4. A stimulation of light-induced proton uptake by phosphate or arsenate, ADP and Mg has been observed. It was not sensitive to concentrations of Dio-9, which eliminated ATP synthesis.
5. 5. The results are seen as inconsistent with the chemiosmotic theory of energy coupling as presently presented. It is suggested that they may be interpreted in terms of a model in which the function of the proton pump is to enable co-transport into the chloroplasts of the negatively charged complex of phosphate, ADP and Mg.
Abbreviations: BDHB, n-butyl-3,5-diiodo-4-hydroxybenzoate; DCMU, (3,4-dichlorophenyl)-1,1-dimethylurea; diquat, 1,1′-ethylene-2,2′-dipyridylium dibromide; FCCP, carbonyl cyanide p-trifluoro-methoxy-phenylhydrazone; HQNO, 2-n-heptyl-4-hydroxyquinoline-N-oxide; PMS, phenazine methosulfate
