LIGHT-INDUCED PHOSPHORYLATION 



435 



have obtained further indications that there may be two sites of phos- 

 phorylation in the bacteria, and that one is by-passed in "the PAIS-path- 

 way". In these experiments, which were made at the Johnson Research 

 Foundation* in Philadelphia, my wife and I were fortunate to have the 

 collaboration of Dr. John Olson of Brandeis University. Experimental 

 details of this work are published elsewhere [15]. As is seen in Table II, 

 the quantum requirement for the formation of one molecule of ATP was 

 about (although not quite) twice as high in "the PMS-pathway " as in 



R. rubrum chromatophores 

 Light 



reductant- 



-»-flavoprotein- 



.PMS, 



HOQNO 

 SN 5949 



antimycin A 



I 



-»-X oxidant 



Vahnomycin 



uncouples | does not 



© 



uncouple 1 







spinach chloroplasts 

 Light 



FMN, FAD 



menadione f \ 



PMS, pyocyaninej I 



reductant ►- flavoprotein- 



.9- 



oxidant — ►- O2 



Valinomycin 



does not |^ 

 ,-'-, uncouple ~^ — 

 uncoupled [ 'P ', { ~P 



Fig. 4. Light-induced phosphorylation. 



"the physiological pathway". This is to be expected if there are twice as 

 many phosphorylation sites in the latter pathway as in the former. 



Some of the preparations used in the studies on the quantum require- 

 ment for ATP-formation were highly active, giving values of 600-700 

 /imoles of orthophosphate esterified per hour per mg. chlorophyll (in a 

 volume of 3 ml.). This was obtained in the absence of any added electron 

 carriers. The bacterial extracts were prepared in the manner reported 



* The generous support of Dr. Britton Chance, head of the Johnson Research 

 Foundation, is gratefully acknowledged. 



