446 



F. GROS 



lOOn 



50- 



per cent protein 



synthesizing 



capacity 



per cent RNA destroyed 



O IO 20 30 



Fig. 6. Protein synthesizing capacity of bacteria as a function of RNA destruction 

 by ribonuclease. To a suspension of E. coli (strain K12) in distilled water and contain- 

 ing 150 jug. of bacteria (dry weight) per milliliters, 200 ng. of crystallized ribonuclease 

 per milliliter are added. After various periods of incubation at 15°C, aliquots are 

 sampled and incubated 10 minutes more at 37°C. in the presence of 1 M NaCl 0.1. 

 Optical densities at 420 m/x, and RNA content per cell are measured at the end of this 

 second incubation period. Treated cells are then chilled, centrifuged, and resuspended 

 in mineral medium containing per milliliter, 10 ng. of S 35 in the form of H2SO4 (specific 

 activity 20,000 c.p.m. per microgram), and glucose (0.2%). Optical densities are ad- 

 justed in each case to that reached after ribonuclease treatment, and cells are incu- 

 bated at 37°C. with aeration. Initial rates of protein synthesis are determined by 

 measuring the tangents to the various curves of S 35 incorporation into the protein 

 fraction. Results of Fig. 6 are expressed in relative initial rates of S 36 incorporation 

 as a function of RNA destruction by ribonuclease. 



tion of the RNA occurs, while the rate of protein synthesis goes on dimin- 

 ishing proportionally to the amount of RNA destroyed (see Fig. 6). The 

 ability to synthesize /3-galactosidase follows exactly the same kinetics. The 

 first rapid drop observed may be based on a more or less specific inter- 

 ference by the ribonuclease with negatively charged components of the 

 cytoplasm (perhaps the soluble RNA) since it is known that protamine, 

 a basic protein of no enzyme activity, can reduce protein synthesis both 

 in living root tips and in bacteria ; the slower decline in protein-syn- 

 thesizing ability which takes place after a longer period of incubation, is 

 probably due to a gradual destruction of the RNA particles. 



It is interesting to note that while alteration in DNA has a more rapid 

 influence on the ability to synthesize 0-galactosidase than the capacity to 

 form peptide material, destruction of RNA influences both these properties 

 at the same rate. It appears therefore that the rate of protein formation, 

 rather than the specificity of the protein formed, is under the control of 

 the stable RNA. 



192 B. P. Kaufmann and N. K. Das, Chromosoma 7, 19 (1955). 



