INDUCED ENZYME FORMATION 



5. Of the forms mentioned above, only T-I„-E can effec- 

 tively and rapidly catalyze enzyme synthesis. 



In the nomenclature of Cohn and Monod (18) T would be 

 an apo-organizer, I, a co-organizer; and T-I, an organizer. 

 The complexes T-E and T-I„-E represent new entities not 

 embraced or employed by their terminology. 



The reversion from positive to negative in "slow adaptors" 

 can be interpreted in terms of the above model in the following 

 manner. As soon as growth in a galactose-free medium occurs, 

 all newly formed templates appear as either T or T-E and con- 

 sequently no enzyme synthesis takes place at them. The tem- 

 plates which were present initially remain as T-I„-E and con- 

 tinue to synthesize enzyme. They are the autocatalysts or active 

 particles and are diluted out by growth. As the reversion 

 growth proceeds, one gets, as a result of the consequent dilution 

 of inducer, some convertible particles, T-E. The ultimate and 

 irreversible decay of active particles if the reversion proceeds too 

 long receives therefore simple explanation in terms of the in- 

 stability of T-E. The anomalous change in stability of active 

 particles (mentioned at the end of IV, B) which occurs late in the 

 reversion is explained simultaneously. 



The conversion to the positive state occurs when a cell con- 

 taining one or more templates of the form T-I„-E or T-E is 

 placed in a medium containing inducer. Any T-E complexes 

 are first converted to T-I„-E and then in both cases free enzyme 

 is formed. By virtue of the enzyme produced other templates 

 can be rapidly converted to the stable T-I„-E state, provided 

 excess inducer molecules are present. The infrequent spon- 

 taneous production of positives from negatives in the "slow" 

 strains might be explained on the basis of the rare occurrence of 

 enzyme formation by unoccupied T or T-I„. 



The novel function attributed to the enzyme and inducer 

 molecules recalls the formally similar hypothesis of the "plas- 

 magene theory." It should be emphasized, however, that 

 the present model exploits a "feed-back" feature which was ac- 

 tually inherent in the plasmagene model but not used. It is the 



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