218 METABOLISM AND PHYSIOLOGY 



system. These results are in agreement with those reported by Kamen 

 and collaborators (3,4), Vernon and Ash (5), and Geller and Lipmann 

 (6) over the past few years. In particular, these results support the 

 recent finding of Bose and Gest (7) showing that dyes such as DPIP 

 may, under certain conditions, overcome an antimycin inhibition of 

 light-induced, cyclic electron transfer. 



As shown in Table 1, when DP A particles are incubated with suc- 

 cinate, one always observes a stimulation of LIP by the addition of 

 catalytic amounts of UQ2. In this particular preparation PMS also 

 greatly stimulated LIP, When succinate and PMS are both present one 

 observes an inhibition which could be considered to result from the 

 over- reduction of some carrier or of the dye. Similarly, in the case 

 where UQ2 stimulated LIP, an oxidation of some component occurred. 

 In agreement with this concept is the fact that UQ2 will relieve some 

 of the inhibition due to over- reduction by succinate (compare vessels 

 3 and 6, Table 1), Further corroboration appears from a comparison 

 of vessels 5 and 6, Table 1, Here again it is reasonable to consider 

 that succinate is acting as an inhibitor by over- reducing a component 

 of the system. 



In the presence of antimycin, LIP stimulation by succinate is com- 

 pletely blocked, whether UQ2 is present or not, PMS- stimulated LIP 



TABLE 1 

 The Effect of Succinate, PMS, UQ2 and Antiniycin on LJP in DPA Particles 



Chromatophore particle preparations were prepared from RhodospiriUum 

 nibruni grown in diphenylamine as previously described (2). Experiments were 

 carried out as follows in Warburg manometer vessels. The main compartment 

 contained 20 ^moles MgCl2,35 yWmoles KH2P04,pH 7.0,100 ^moles giycylgly- 

 cine buffer, pH 7.4,40 //molesof glucose, 0.5 mgof hexokinase (Sigma type III), 

 0.8 mg of chromatophore particle protein and additions as indicated above. 10 

 //moles of ADP were in the side arm. Total volume, 2.5 ml. The cups were filled 

 in the dark and gassed with pre-purified nitrogen for 5 minutes. Then the ADP 

 was tipped and the light (1200 ft-candles on each vessel) was turned on. At the 

 end of the incubation period (usually 45 minutes or 1 hour) the reaction was 

 stopped and phosphate uptake determined as previously described (2). The fig- 

 ures in the table represent micromoles of phosphate esterified in 1 hour. The 

 additions consisted of 2 //moles succinate, 0.03 mg PMS, 3 fug antimycin, 0.08 

 //moles of UQ2 in 5 microliters alcohol. 



