ATPaSE IX OXIDATIVE PHOSPHORYLATION 



249 



This material is heat-stable, precipitable by trichloroacetic acid and 

 nondialvzable. The possibility that this substance may restore the ADP- 

 ATP exchange by masking the hydrolytic site of the ATPase and thus 

 convert it to a transfer enzyme is being explored. 



Finally, we would like to present the results of some recent attempts 

 to resolve further the submitochondrial particles. If the particulate fraction 

 which is recoupled by the ATPase is further disintegrated by sonic oscilla- 

 tion, a new particle is obtained (residue 2) which requires both the super- 

 natant fluid from which these particles were separated as well as the 

 purified ATPase in order to restore phosphorvlation. These results are 



TABLE VIII 



The Requirement of Factor 2 for Oxidative Phosphorylation Catalyzed 



BY Residue 2 



Experimental conditions as described in the text and [4]. Factor 2 was added 

 directlv to the vessels. 



Residue 



Coupling 

 Factor i 



Factor 2 



JO 



AP: 



P:0 



presented in Table VIII. The top half of the table merelv shows the 

 response of the original particles to the purified ATPase or as it is referred 

 to here, coupling factor i. The lower portion of the table shows that both 

 the ATPase and the supernatant solution obtained after sonic disintegra- 

 tion (factor 2) is required to restore oxidative phosphorvlation. Factor 2 is 

 heat-labile, non-dialyzable, is precipitated at pH 5-4 and exhibits no 

 ATPase activity. It does not catalyze either the ''-P, ATP or the ADP- 

 ATP exchange even when supplemented with the ATPase, but is required 

 together with the ATPase for the restoration of a dinitrophenol sensitive 

 ^'■^P,-ATP exchange to the particles. 



Little is known concerning the mechanism bv which the ATPase is 

 linked to the electron transport chain, nor is anvthing known of the 

 enzymic function of factor 2. Nevertheless, the resolution of the enzvmes 

 of oxidative phosphorylation represents a necessarv first step toward the 

 ultimate goal of demonstrating the mechanisms of this complex process. 



