233 



C. C. Black and A. San Pietro 



.05 .10 .15 .20 



ml of CHROMATIUM Foctor 



UJ -40 

 a: 



Fig. 7. (Left) Effect of Chromatium phosphodoxin on photophos- 

 phorylation with spinach chloroplast fragments. 

 Fig. 8. (Right) Effect of spinach phosphodoxin on EPR signals 

 of spinach chloroplast fragments. Cuive 1 - Dark; chloroplasts 

 alone. Curve 2 - Dark; chloroplasts plus phosphodoxin. Curve 

 3 - Light; chloroplasts plus phosphodoxin. Curve 4 - Light; 

 chloroplasts alone. 



In summary, we have isolated a new naturally occurring, thermostable, 

 water-soluble catalyst (phosphodoxin) of photophosphorylation which appears 

 to be ubiquitous among photos yn the tic organisms. Phosphodoxin from each 

 photos ynthetic organism appears to be active with both chloroplast and 

 chromatophore fragments. Spinach phosphodoxin alone has a light- induced 

 EPR signal and in combination with spinach chloroplast fragments decreases 

 the dark EPR signal and increases the light EPR signal, and contributes 

 primarily to signal 2. 



This is Contribution No. 

 Laboratory. 



129 from the Charles F. Kettering Research 



REFERENCES 



1. Frenkel, A., J. Am. Chem. Soc. , 76, 5568(1954). 



2. Arnon, D. I., M. B. Allen, F. R. Whatley, Nature, n4, 394(1954). 



3. Geller, D. M. , and J. D. Gregory, Federation Proc. , J^, 260(1956). 



4. Jagendorf, A. T. , and M. Avron, J. Biol. Chem., 231, 277(1958). 



5. Hill, R. , and D. A. Walker, Plant Physiol. , 34, 2415T1959). 



6. Arnon, D. I. , F. R. Whatley, and M. B. Allen, Science, 127, 1026 



(1958). 



7. Jagendorf, A. T. , Federation Proc. , 18, 974(1959). 



