632 



R\ifus Lumry 



small amounts of free -energy necessary for oxygen production can be brought 

 about in this way. 



In conclusion we may observe that the suggestions for mechanical mechan- 

 isms in photosynthesis are rather large departures from current approaches 

 to mechanisms. There is in the literature abundant suggestions of conforma- 

 tional change during enzymic function (for pertinent examples see Ref. 34). 

 These changes may prove to be real and large, but if our studies have any 

 general significance,they will prove to be small on close investigation, though, 

 of course, the small changes may be vitally important in the catalytic process. 

 Enzyme chemistry is just beginning to move into the era of real mechanism 

 study and it is probable that a good bit of work will have to be done on single 

 enzymes before we have sufficient information to allow any profitable analysis 

 of the detailed mechanism of photosynthesis. We do not yet know whether the 

 integrity of the granum is essential for the process since the many failures to 

 find reactions in detergent -treated preparations and in similar fractionation 

 experimentsare hardly proof of the need for integrity. The studies from the 

 Enzyme Institute at Wisconsin suggest that only sub-particles of the mitochon- 

 drian need have structural integrity.'-^-*) It is highly desirable that similar 

 investigation of the granunn be carried out. 



We caution against the ready explanation of peculiar aspects of photosyn- 

 thetic sub-processes as being "due to protein conformation change. " On the 

 other hand we are convinced that at the present tinne the best place to look for 

 the unique basis of protein reactions is in conformational factors. We must 

 continue to ask why Nature has made use of well-knit, highly organized 

 particulate structures for both oxidative phosphorylation and photosynthesis. 

 We must continue to inquire into the meaning of the experiments of Packer^ ' 

 and of Izawa, Itoh and Shibata. '^) 



Acknowledgement: This work was supported by the U. S. Atomic Energy 

 Commission through contract AT(1 1 -l)-894. 



BIBLIOGRAPHY 



1. For example, F. Erhardt and E. W. Abrahamson, Abstracts 145th Meeting 

 American Chemical Society, Sept, 1963, 68C; M. Keyes, F. Juergens, 



G. Maggio and E. W. Abrahanmson, ibid. 47C. 



2. E, Weinbach, A. Shef ield and J . Garbus, Proc. Natl. Acad, Sci. (U.S.) 50, 

 561 (1963). 



3. A. Lehninger, J. Biol. Chem. 234 , 2465 (1959). 



4. J. Rieske, Biochem. Biophys. Res. Comm. 8^, 421 (1962). 



5. L,. Smith, personal communication. 



6. L. Packer, Biochem. Biophys. Res. Comm. % 355 (1962); L. Packer, 

 Y. Mukohata and R. Marchant, Federation Proc. 23^, 588 (1963). 



7. M. Itoh, S. Izawa and K. Shibata, Biochim. Biophys. Acta 66^, 319 (1963); 

 also two papers to appear in 1963. 



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