440 F. GROS 



V. Protein Synthesis After Selective Destruction or Removal of a 



Nucleic Acid 



The fact that specific protein can be formed in a cell without a correspond- 

 ing increase in its nucleic acid content, restricts the choice of hypotheses 

 on the nature of the relationship between protein and nucleic acid. This re- 

 lationship appears therefore to be catalytic rather than stoichiometric, and 

 it suggests that the capacity to synthesize protein depends on the presence 

 or the integrity of the nucleic acid rather than on its net synthesis. 



1. Enzyme and Protein Synthesis After Transmutation of the 

 Phosphorus Atoms in Bacterial DNA 



The size of the bacteria does not allow enucleation experiments of the 

 type performed with algae or amoebae. In enucleated portions of Acetabu- 

 laria mediterranae, protein synthesis can take place for quite a long 

 time. 166 ' 167 For example, C 14 2 or glycine-C 14 are incorporated at a normal 

 rate into the protein fraction and a net increase in the protein mass is also 

 observed. 168 RNA synthesis has also been reported in the nucleated frag- 

 ments. 167 In amoebae, the situation is rather different, since, according to 

 Mazia, 169 removal of the nucleus leads to an immediate diminution (40 to 

 50 %) in the rate of protein synthesis as measured by incorporation of ra- 

 dioactive methionine. The situation in relation to RNA synthesis is still 

 debatable, since, according to Skreb 170 and to Plaut and Rustad, 171 enu- 

 cleation of amoebae does not suppress incorporation of adenine-C 14 or 

 orotic acid-C 14 into the RNA, while according to other workers 172 it sup- 

 presses the incorporation of uracil-C 14 . 



Even if conflicting results and the possibility of artifacts have to be taken 

 into consideration, it seems reasonable to conclude that in the absence of 

 its nucleus, the cytoplasm can still incorporate amino acids into peptide 

 linkages. The mechanism by which an enucleated fragment can perform 

 enzyme synthesis has also been studied. 



According to Baltus, 173 enucleated halves of A. mediterranae can synthe- 

 size aldolase at an almost normal rate. It is not known, however, whether 

 such enucleated fragments can form the enzymes which are normally asso- 



166 J. Brachet and H. Chatrenne, Nature 168, 950 (1951). 



167 J. Brachet and H. Chantrenne, Cold. Spring Harbor Symposia Quant. Biol. 21, 

 329 (1956). 



168 F. Vanderhaeghe, Biochim. et Biophys. Acta 15, 281 (1954). 



169 D. Mazia and D. M. Prescott, Biochim. et Biophys. Acta 17, 23 (1955). 



170 R. Skreb, quoted by Brachet and Chantrenne. 167 



171 W. Plaut and R. C. Rustad, Biochim. et Biophys. Acta 33, 59 (1959). 



172 D. M. Prescott, Expll. Cell Research 12, 196 (1957). 



173 E. Baltus, Biochim. et Biophys. Ada 33, 337 (1959). 



