277 



R. A. Dilley, M. D. Henninger and F. L. Crane 



pyridine nucleotide reductase (PPNR). The restoration of cytochrome c 

 reduction by e^-tocopherylquinone and by the PQ-C +PQ-D mixture also re- 

 quires addition of PPNR as does the PQ-A + PQ-D + PQ-C dependent reduction 

 of NADP. The photooxidation of reduced NADP which occurs when PQ-A is 

 added to extracted chloroplasts is also stimulated by addition of PPNR. 



These results lead us to the proposal that there are several sites for 

 quinone function in chloroplasts which show considerable specificity with 

 regard to quinone type. Further experimentation will be necessary to 

 determine the site of function of each of these quinones. 



This research was supported in part by Grants GM08025 and GM10741 

 from the National Institutes of Health and by Grant GB567 from the National 

 Science Foundation. 



ACKNOWLEDGEMENTS 



We wish to thank Dr. L. E. Mortenson of this department for highly 

 purified photos yn the tic pyridine nucleotide reductase and Dr. S. R. Ames of 

 Distillation Products Industries for samples of tocopherols. 



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