274 Discussion 



yeast cell there are many functions, e.g. protein synthesis, taking place 

 in the cytoplasm. In the case of muscle it is possible to do a higher 

 level of work under aerobic than under anaerobic conditions, at a 

 sustained rate. Is it not necessary to make an ad hoc theory to explain 

 how the ATP, which is not in the cytoplasm as far as the phospho- 

 fructokinase is concerned, is in the cytoplasm as far as certain functions 

 are concerned? I agree that the endoplasmic reticulum offers an 

 attractive way out of the dilemma, but I insist that it is an ad hoc 

 hypothesis. 



Lynen: There is the possibility that the Michaelis constants for the 

 various processes differ. If the affinity of ATP for the protein-synthesiz- 

 ing enzyme were greater than for the phosphofructokinase, protein 

 synthesis could occur at normal rates whereas the phosphorylation of 

 phosphofructose would be retarded. 



Coxon: A point relevant to the possible interaction of ATP in the 

 mitochondria on the one hand, and the cytoplasm on the other, and one 

 which draws on some electrophysiological evidence of a different kind 

 from what we have been discussing up to now, is the observation that one 

 can reduce the sodium efflux in the invertebrate nerve by soaking it in 

 cyanide (Caldwell, P. C, and Keynes, R. D. (1957). J. Physiol, 137, 12) 

 or in DNP (Keynes, R. D. (1959). Proc. IV int. Congr. Biochem., in 

 press) ; this is accompanied by lowering of the total ATP. On the other 

 hand, after cyanide poisoning, one can restore the efflux by introducing 

 ATP through an intracellular micro-injector; however, they did find 

 that the restoration of the flux for a given concentration of ATP was 

 less when that had been introduced from the outside, which suggested 

 (Hodgkin, A. L. (1957). Proc. roy. Soc. B, 148, 1) that they had not got 

 it in quite the right place to give the maximum effect. 



Holton : If a reversible transfer of ATP, ADP and inorganic phosphate 

 in and out of the mitochondria really occurs, as has been postulated in 

 connexion with the mechanism of the Pasteur effect, the movement of 

 these substances might be accompanied by changes in mitochondrial 

 shape or volume, and might thus be amenable to detection and study by 

 optical methods. Dr. Beechey and I have recently made some observa- 

 tions on heart sarcosomes which show that a rapidly reversible swelling 

 and shrinking phenomenon does indeed occur in these particles and that 

 its properties are those to be expected from a transfer process linked 

 closely with oxidative phosphorylation. 



Relationships between transfer of material, morphological changes 

 and active metabolism in mitochondria and sarcosomes have been 

 reported by a number of workers (e.g. Bartley, H., and Davies, R. E. 

 (1952). Biochem. J., 52, 20; MacFarlane, M. G., and Spencer, A. G. 

 (1953). Biochem. J., 54, 569; ChappeU, J. B., and Perry, S. V. (1954). 

 Nature (Lond.), 173, 1094; Beyer, R. E., Ernster, L., Low, H., and 

 Beyer, T. (1955). Exp. Cell Res., 8, 586), while recently it has been 

 shown (Lehninger, A. L., and Ray, B. L. (1957). Biochim. biophys. 

 Acta, 26, 643) that a close link exists between the oxidation state of the 

 respiratory chain of liver mitochondria and the occurrence of phos- 

 phate-induced swelling. In our experiments we have studied a particular 



