272 ('. V. WHITTINGHAM 



oxygen, is inherently a property only of whole chloroplasts. This is what Ohmura 

 finds in his latest paper cited by Dr. Whittingham. 



Brown: Broken fragments of chloroplasts contaminated with mitochondria 

 could be doing phosphorylation. 



Amon : Yes, I am coming to that. 



The mitochondria do only oxidative phosphorylation. But a "chloroplast frag- 

 ments" preparation which contains both broken chloroplasts and some mito- 

 chondria can do both tj^jes of phosphorylation. The concept is very simple: there 

 are two sites of phosphorylation in the cell, one strictly light-dependent, which is 

 the property of the whole chloroplast, and the other independent of light but de- 

 pendent on oxygen. The latter type, i.e., oxidative or respiratory chain phosphoryl- 

 ation localized in mitochondria keeps the cell going at night when the light is off. 



To sum up, the green preparations known as "chloroplast fragments" are usu- 

 ally capable of the Hill reaction and also under certain conditions of some photo- 

 synthetic phosphorylation because they contain chloroplast material. These prepa- 

 rations may also be capable of oxidative phosphorylation because they contain 

 mitochondria. 



But the significant point, which is also reported in his last paper by Ohmura and 

 explains his previous results, is the fact that whole chloroplasts do only photo- 

 synthetic phosphorylation when they are uncontaminated by other particles. 



How much of each tj'pe of phosphorylation will be found in a given preparation 

 depends on the relative proportions and activities of these two different compo- 

 nents, one derived from chloroplasts and the other consisting of mitochondria. 



Whittingham : I just want to ask for a point of information. Suppose you take a 

 preparation of whole chloroplasts and throw away all the small particles and then 

 break the whole chloroplast preparation. Will you find that the fragments from the 

 whole chloroplast preparation exhibit properties which were not exhibited by the 

 whole? For example, one might assay cytochrome c oxidase activity ; have you done 

 this e.xperiment? 



Amon : Broken chloroplasts which have been prepared not from a mixed fraction 

 but from a pure preparation of whole chloroplasts show only photosynthetic phos- 

 phorylation. However, we have prepared from the same spinach leaves three types 

 of particles: whole chloroplasts, an intermediate fraction containing broken chloro- 

 plasts and mitochondria, and a third fraction containing all particles put together. 

 We got oxidative phosphorylation or photosynthetic phosphorylation or both 

 depending on how much of each component was present in the preparation. 



References 



1. Davenport, H. E., Hill, R., and T^Tiatley, F. R., Proc. Roy. Soc. (London), 



B139, 346 (1952). 

 la. Davenport, H. E., and Hill, R., Proc. Roy. Soc. (London), B 139, 327 (1952). 



2. Davenport, H. E., and Hill, R., Resumi Commxins. Shne Congr. intern, hio- 



chim. Brussels (1955). 



3. Warburg, O., and Krippahl, G., Z. Naturforsch., blO, 301-304 (1955). 



4. Brown, A. H., and Franck, J., Arch. Biochem., 16, 55 (1948). 



5. Amon, D. I., Allen, M. B., and Whatley, F. R., Nature, 174, 394 (1954). 



