Pyocyanine and Phosphorylation with Chloroplasts.

The process of formation of oxygen by illuminated chloroplast preparations in presence of added Hacceptors resembles the converse of the process of the oxidation of H-donors by oxygen with the KeilinHartree muscle preparation derived from mitochondria (9). In the former process the H-transport is against the chemical potential owing to transformation of the light energy. The discoveries of the photosy-nthetic phosphorylation with chloroplast preparations by Arnon, Whatley and Allen (2) and with the chromatophores from a photosynthetic bacterium by Frenkel (4) were of supreme significance in the development of the biochemical study of photosynthesis. Furthermore they indicated a similarity of the chloroplast to the mitochondria which was already partly apparent from the comparative study of cytochrome components in the two subcellular structures (10, 11). In oxidative phosphorylation with mitochondria the H-transport is dependent upon the presence of both inorganic phosphate and an acceptor for the phosphate group. A similar condition has been shown to operate in the chloroplast by Arnon, Whatley and Allen (6). The reduction of an H-acceptor and concurrent 02 production by the illuminated chloroplast system is to a very significant extent coupled with phosphorylation. Moreover the phosphate acceptor-adenosine diphosphate (ADP)-is the same for the chloroplasts and the mitochondria. With mitochondria the coupling of H-transport and phosphorylation can be removed either by the presence of certain reagents or by the treatment used for the Keilin-Hartree preparation. In such a case active H-transport is shown without any concurrent phosphorylation. An analogous process of uncoupled H-transport is shown by the chloroplast preparations (4, 16, 17) either by addition of reagents or by a physical treatment. The important difference between chloroplasts and mitochondria apparently is in the direction of hydrogen transport and it might be legitimate to ternm the phosphorylation with chloroplasts as "reductive" in contrast to the oxidative phosphorylation with mitochondlria. It has been shown that phosphorylation can occur with chloroplasts in light without any 02 pro(luction and without the corresponding stoichiometric reduction of any Hacceptor. Thus a situation, named by Arnon "cvclic phosphorylation," would seem to involve a reduced