304 A. W. FRENKEL 



ential centrif ligation, the material sedimenting at 60,000 X g 

 (for 1 hour) contains most of the phosphorylating activity which can 

 be induced in the light, but this activity can be elicited from a well- 



TABLE I. Requirements for Light-Induced Esterification of Orthophosphate by 

 Cell-Free Preparations of Rhodospirillum rubrum under Anaerobic Conditions 



A. Crude cell-free preparations B. Partially purified preparations 



(Supernatant from sonically disinte- Crude preparation obtained as indi- 

 grated material after centrifugation for cated under (A), then centrifuged at 

 V2 hour at 25,000 X g). 60,000 X g for 1 hour. Sediment re- 



suspended in 0.2 M glycylglycine at 

 pH 7.5. Centrifuged again at 60,000 X 

 g for 1 hour and resuspended in glj^cyl- 

 glycine buffer pH 7.5. 



Requirements 

 1, Orthophosphate 



3, Acceptors of high-energy phosphate 



Adenosine-5 '-phosphate (Adenosine-5 '-phosphate active only 



with the following additions: trace of 

 ATP; adenylate kinase preparation 

 from R. rubrmn, present in the super- 

 natant of the crude preparation after 

 centrifugation for 1 hour at 144,000 X 



g). 

 Adenosine-5 '-diphosphate 

 Inosine-5 '-diphosphate 

 2b. Substances inactive as acceptors of high-energy phosphate produced by the 



photolytic system 



Adenosine-5 '-phosphate, except with 

 additions as indicated under (2) 

 Adenosine-3 '-phosphate (± trace of ADP or ATP) 

 Inosine-5 '-phosphate (± trace of ADP, ATP, or IDP) 

 Uridine-5 '-phosphate (=b trace of ADP or ATP) 

 Creatine (± trace of ADP or ATP) 



3. Additional requirements in the presence of ADP as acceptor of high-energy 



phosphate 

 None observed thus far Mg'*"''' at a concentration of about 



5 X 10-3 mole per liter; DPNH, less 

 than 0.01 mole per mole of orthophos- 

 phate esterified; or traces of succinate, 

 lactate, etc. (ref. 4) 



4. Substances which have little or no effect on the rate of light-induced phos- 

 phorylation by crude or partially purified preparations in the presence of ADP 



and minimum requirements as listed under S 



