94 SUBCELLULAR PARTICLES 



Table 4. Molecular ratios of oxidation-reduction components in etp 

 Succinic ilchydrog. flavoprotein i 



DPNH dchydrog. flavoprotein i 



C\tochrome a 2 



Cytochrome h 

 Cytochrome c -\- c\ 

 Copper 

 Coenzyme Q 



copper. The lipid content is 35 per cent by weight. The electron transport particle 

 can be isolated in a variety of ways, and regardless of the method of isolation the 

 composition of the particles in terms of the basic components is remarkably 

 constant. 



The stoichiometry of the components in the electron transport particle is sum- 

 marized in table 4. The two flavoproteins are present in equal amounts. For each 

 2 moles of flavoprotein there are 2 moles each of cytochromes b and a and ap- 

 proximately I mole each of cytochromes Cx and c. It is of interest that the electron 

 transport particle of Azotobacter vmehnidii which Dr. Bruemmer in the Depart- 

 ment of Bacteriology under Professor Perry Wilson has isolated (7) shows great 

 similarities in enzymatic activity and stoichiometry to the corresponding particle 

 of beef heart (table 5). There is thus some experimental support for the concept 

 of the electron transport particle as a fundamental unit of mitochondrial function. 



By a variety of procedures, all of which involve reagents which react with lipid, 

 the electron transport particle can be fragmented into derivative particles. A sum- 

 mary of the components in a few such particles is given in figure 8. The succinic 

 dehydrogenase complex (16, 3) contains cytochromes b and <ri but no cyto- 

 chrome a. This is a red particle. The flavoprotein present in the succinic dehy- 

 drogenase complex is predominantly succinic dehydrogenase. An analogous particle 

 called the succinic-DPNH dehydrogenase complex has much the same com- 

 position except that the two flavoproteins, the succinic and DPNH dehydro- 

 genases, are both present in equal amounts as in ETP (29). A green particle 

 has been prepared by Crane and Glenn (9) which has the complete respiratory 

 chain for DPNH but has essentially no capacity for oxidation of succinate. There 



Table 5. Comparison of etp from beef heart and a. vinelandii 



