Electron Transport and Phosphorylation in 

 Light-Induced Phosphorylation* 



Herrick Baltscheffsky 



The Wenner-Gren Institute for Experimental Biology, 

 University of Stockholm, Szveden 



For some time we have been studying light-induced phosphorylation 

 (photosynthetic phosphorylation, photophosphorylation) in photosynthetic 

 bacteria and also, to some extent, in green plants. In these studies inhibitors 

 of oxidative phosphorvlation in animal mitochondria have been employed, 

 in an attempt to obtain information about electron transport and phos- 

 phorvlation reactions in light-induced phosphorylation, both per se and as 

 compared with the svstem for oxidative phosphorylation. 



Washed chromatophores of Rhodospirillum rubrum were used in the case 

 of bacteria and washed spinach chloroplasts in the case of green plants. In 

 these two systems light-induced phosphorylation was discovered about 6 

 years ago, first by Arnon et al. [i] in plants and, somewhat later, by 

 Frenkel [2] in bacteria. In fact, most of the present knowledge about the 

 light-induced formation of adenosine triphosphate (ATP)| stems from 

 studies with these materials. 



Some results from our earlier investigations, which were made at high 

 light-intensities and under aerobic conditions and which have been described 

 in detail recentlv [37], ^vill be summarized in the first two figures. 



Figure i shows our proposed scheme for the electron transport in light- 

 induced phosphorylation of R. rubrum [3]. The sites of action of certain 

 inhibitors and of the stimulatory agent phenazine methosulphate (PAIS) 

 are also indicated. As is seen from the Figure, it is possible in this bacterial 

 system to choose between two pathways for the electron transport. In what 

 may be called "the physiological pathway " it is assumed that the electrons 

 are transferred from the photochemical reductant to flavoprotein and 



* This work has partly been carried out in collaboration with Mrs. M. Balt- 

 scheffsky (mainly in experiments with bacteria) and Miss B. Arwidsson (mainly 

 in experiments with plants). 



t Abbreviations : ATP, adenosine triphosphate ; DPNH, reduced diphospho- 

 pyridine nucleotide; FAD, flavinadenine dinucleotide ; FMN, flavin mono- 

 nucleotide; PMS, phenazine methosulphate; HOQNO, 2-/?-heptyl-4-hydroxy- 

 quinoline-N-oxide ; m, moles per litre; LIP, light-induced phosphorylation. 



