Control Points in Phosphorylating Respiration 141 



It is now well known that in the absence of ADP freshly- 

 prepared mitochondria respire very slowly, but that addition 

 of DNP causes release of respiration. Such release of respira- 

 tion presumably is caused by the discharge of high-energy 

 intermediates of the carriers by DNP, such as the carrier /^ X 

 of reaction (1). These phenomena are also observed with the 

 digitonin fragments of mitochondria ; DNP causes stimulation 

 of ADP-less respiration to a limiting level which is exactly the 

 maximum rate given by addition of ADP itself. Preparations 



Table III 



Action of R factor on partial reactions of 



OXIDATIVE phosphorylation 



Test systems for the assays as described by Wadkins and Lehninger (1959). 

 The concentration of R factor preparation added was approximately three 

 times the concentration just necessary to produce maximal respiratory 

 stimulation (see text). 



Addition of 

 Reaction Quantity measured Control R factor 



of the R factor also show this action, as shown in Table IV, 

 the release of respiration being roughly proportional to the 

 amount of R factor added. 



However the respiration-releasing activities of DNP and R 

 factor are quite different in nature. A concentration of DNP 

 just adequate to release respiration maximally, when added 

 to a parallel test system containing ADP, produces sub- 

 stantially complete uncoupling of phosphorylation. On the 

 other hand, concentrations of R factor preparation which just 

 produce complete release of respiration in an ADP-less system 

 produce only partial and often very little uncoupling of 

 phosphorylation when tested in a system containing ADP, as 

 is shown by the P/O ratios in Table IV. It is of significance 

 that different preparations of R factor vary in their relative 



