S. SPIEGELMAN AND A. M. CAMPBELL 



recognition that enzyme molecules can serve to activate un- 

 occupied templates that permits an explanation of autocatalysis 

 which does not invoke self-duplication. There are no data 

 existent to our knowledge which demand this latter property as 

 an integral part of the enzyme-forming process. It would, however, 

 seem necessary to retain self-duplication as a method of tem- 

 plate maintenance to explain the instances of cytoplasmic trans- 

 mission noted, particularly in the case of the "petite" mutants. 



Stages in the Induced Formation of Enzyme 

 and Their Interpretation 



The particular appeal of the model just proposed lies in the 

 fact that it is in principle applicable to systems other than "slow 

 adaptation" and permits an instructive interpretative compari- 

 son among them. A central feature is the assumption that the 

 active enzyme-synthesizing unit is the triple complex between 

 template, enzyme, and the inducer. The difference between 

 the slow adaptors and the normal variety will then be explained 

 in terms of the very much lower probability of an unoccupied 

 template of the slow type producing an enzyme molecule in the 

 absence or the presence of inducer. In normal varieties this 

 event occurs sufficiently frequently in the absence of inducer so 

 that at any given moment it is highly probable that there is at 

 least one T-E complex present per cell. This represents there- 

 fore the constitutive mechanism for the synthesis of the low 

 basal enzyme levels frequently observed in inducible strains. 

 In the same vein, one can explain the so-called "constitutive 

 mutants" (17,46) which make enzyme in inducer-free medium 

 even faster than the normals do in the presence of inducer. 

 Thus, one can suppose that "constitutive mutants" possess 

 templates that possess an even higher than normal probability of 

 spontaneously forming enzyme molecules. This has the ob- 

 vious consequence that constitutive enzyme formation of this 

 variety should more closely approximate noninduced enzyme 

 synthesis. Some constitutive enzyme formation is of course 

 referable to internal inducer production, as is beautifully shown 



146 



