Metabolic Control of Structural States of Mitochondria 



Lester Packer 



Departtnent of Microbiology, 



University of Texas Southwestern Medical School, 



Dallas, Tex., U.S.A. 



I would like to discuss briefly certain properties of the swelling-shrink- 

 ing phenomenon as it occurs /// vitro and perhaps in the living cell. 

 Although many of the questions surrounding this phenomenon are un- 

 answered, some experiments suggest directions in which explanations 

 may lie. 



Sub- 

 strate 



Z 

 PN 



FP 



Cr 



^ Oxygen I 



A. ' >■ 



-n Carrier~I ■- 



I 

 X~I 



X~P 





ATP 



Fig. I. Scheme for oxidative phosphorylation. The components of the mito- 

 chondrial membrane are enclosed bv the dashed line. 



In particular there are two points I would like to raise, both are still 

 speculative, but it appears that their clarification may contribute to our 

 understanding of the phenomenon at the macromolecular and cellular 

 levels. The first is that it seems certain that changes in mitochondrial 

 volume can be directed in vitro by the activity of the enzymes of the 

 respiratory chain and oxidative phosphorylation. The system is schematized 

 in Fig. I. The reactions enclosed by the dashed lines represent the res- 

 piratory chain and associated enzymes of the coupling mechanism located 

 in the membrane. This outline embodies current concepts of several 

 laboratories [i, 2] in which it is thought that following electron transport 



