Protein Synthesis in Protoplasts 187 



protoplasts. We shall return subsequently to the significance 

 of the results with the two nucleolytic enzymes. 



The first extensive investigation of incorporation in defined 

 protoplast preparations was performed by McQuillen (1955a). 

 A variety of ^^C-labelled compounds was used, and a com- 

 parison of intact cells and protoplasts was made. The results 

 obtained in the two were qualitatively similar. Thus, ^^C- 

 carboxyl-labelled glycine made its way into the protein 

 glycine and also into the adenine and guanine of the nucleic 

 acids. The rate of incorporation in protoplasts was between 

 50 and 100 per cent of that observed in intact cells. 



About the only striking difference between cells and proto- 

 plasts which emerged in these studies was a curious and un- 

 explained dissimilarity in response to uranyl chloride. It was 

 found that UO2CI2 suppressed the incorporation of glycine 

 into the nucleic acids of protoplasts but had no effect on the 

 metabolism of intact cells. 



Induced Synthesis of Protein 



The induced synthesis of enzymes in suspensions of proto- 

 plasts was simultaneously achieved in three laboratories. 

 Wiame and his collaborators (1955) showed that arabinokinase 

 was formed in protoplasts prepared from Bacillus subtilis when 

 they were incubated aerobically in the presence of arabinose, 

 (NH4)2S04, yeast extract, and NaCl at 0* 5m as a stabilizing 

 agent. McQuillen (19556, 1956) and Landman and Spiegelman 

 (1955) demonstrated that protoplasts of B. 7negaterium strain 

 KM can be induced to synthesize a (B-galactosidase. I should 

 now like to summarize the principal properties of this latter 

 system. Unfortunately, McQuillen' s findings have not as yet 

 appeared in extenso and so comparison of the data obtained in 

 the two laboratories is impossible. 



Since they have already been detailed elsewhere (Landman 

 and Spiegelman, 1955), we need not entertain here an exten- 

 sive description of the conditions and stabilizing medium 

 which were found to permit p-galactosidase formation in 



