250 MAYNARD E. PULLMAN, HARVEY S. PENEFSKY AND E. RACKER 



References 



1. Pullman, M. E., Penefsky, H. S., and Racker, E., Arch. Biochem. Biophys. 76, 

 227 (1958). 



2. Penefsky, H. S., Datta, Anima, and Pullman, M. E., Fed. Proc. 18, 300 (1959). 



3. Pullman, M. E., Penefsky, H. S., Datta, Anima, and Racker, E., J. biol. 

 Chem. 235, 3322 (i960). 



4. Penefsky, H. S., Pullman, M. E., Datta, Anima, and Racker, E.,^. biol. Chem. 

 235» 3330 (i960). 



5. Green, D. E., Lester, R. L., and Ziegler, D. M., Biochim. biophys. Acta 23, 

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6. Nossal, P. M., Aiist.J. exp. Biol. med. Sci. 31, 583 (1953). 



7. Linnane, A. W., Biochim. biophys. Acta 30, 221 (1958). 



8. Lardy, H. A., and Elvehjem, C. A., Annu. Rev. Biochem. 14, i (1945). 



9. Hunter, F. E., Jr., in "Phosphorus Metabolism", ed: W. D. McEIroy and B. 

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10. Lardy, H. A., and Wellman, W.^J. biol. Che?u. 201, 357 (1953). 



Discussion 



CoNOVER : As the cold lability of the ATP-ase might suggest a lipoprotein of 

 some sort, I was wondering if you have checked the lipid contents of the protein ? 



Pullman: No we haven't; until recently we haven't been able to obtain the 

 amount of purified enzyme required for many of the physical and chemical deter- 

 minations which we would like to carry out. We think we have now solved this 

 problem and plan to examine this aspect of the problem in the near future. 



Conover: Also I might add that I have tried to demonstrate ADP-ATP 

 exchange in magnesium-stimulated ATP-ase as prepared by Kielley and Kielley, 

 and we have run into similar difficulties in trying to find an exchange in this 

 enzyme. 



Lardy: It is very interesting that />-mercuribenzoate inhibits the DNP portion 

 of the ATP-ase. This is a property which is shown in partly aged mitochondria. 

 We have found several years ago that we could inhibit endogenous ATP-ase activity 

 and in some experiments with these mitochondria it actually increased; it did, 

 however, eliminate the DNP-stimulated portion. 



Pullman : In a few experiments we too have observed that PCMB stimulated 

 the magnesium activated portion of the activity. However, by far the most consis- 

 tent effect of PCMB was to eliminate the DNP stimulation without affecting the 

 Mg++ activation. 



Lehninger : It seems to me that the factors which Dr. Pullman and I have been 

 studying in our laboratories are coming closer and closer together. I think we also 

 share the view that this coupling mechanism has its critical point where the water 

 site is created, possibly by an inhibitor such as U factor. I would like to suggest, 

 however, the possibility that his coupling factor or ATP-ase is a complex enzyme 

 in the same sense as actomyosin is, and is composed of two or more pieces. I have 

 been thinking myself that our C factor is similar to your ATP-ase and that it in turn 

 consists of two components one which may be M, and of course it will take further 

 work to clarify all these things. One point I wanted to ask you was when you have 



