Protein and Polynucleotide Turnover 211 



to do with inhibition of nucleic acid synthesis seems however 

 to be doubtful, according to information from G. B. Brown. 

 We intend to study these inhibitions with the help of tracer 

 methods. 



We regard our results as definite in one respect, namely the 

 correlation and time sequence in the general pattern of nucleic 

 acid-protein synthesis. Our experiments cannot elucidate 

 the underlying mechanism because they are preliminary and 

 incomplete, and the enzyme systems were not studied at all. 

 There are indications that it would be advisable to study a 

 third group of substances, the phosphatides, which are 

 apparently closely connected with nucleic acids and proteins 

 in the cell, and we are intending to extend our investigations 

 to these substances. Our reasons for this are mainly specula- 

 tive. One of us, S. Aqvist, recently found that Avith [^^N] 

 glycine as a precursor the amino-acids or peptides to be found 

 in the phosphatide fractions of the liver are highly marked 

 with ^^N. At different regeneration times the values are about 

 the same as those which would be expected if this glycine 

 represented the precursor at the site of incorporation. 



DISCUSSION 



Rittenberg: Do I understand you to state that the synthesis of the 

 nucleoproteins not only precedes the synthesis of the proteins but it is 

 necessary for their synthesis? 



Hammarsten: That is what we are trying to show, and I think that 

 these experiments go some way toward showing it. Maybe the Hitchings 

 experiment with different purines would also show that you can inhibit 

 protein synthesis without inhibiting nucleic acid synthesis, but that 

 you cannot inhibit nucleic acid synthesis without inhibiting all the 

 protein synthesis. It might be so. 



Brown: I think that a lot of the confusing points about the ratio of 

 incorporation of isotope into adenine and guanine are now solved. It 

 seems from your work that much depends on the time interval involved. 



You referred to diaminopurine and other purines inhibiting the growth 

 of Lactobacillus casei. We have been working with Dr. Hitchings 

 lately on the purine metabolism pattern of Lactobacillus casei, an organism 

 which very readily converts guanine into adenine or vice versa; if you 

 give the organism both, it makes about half of its guanine into adenine 

 and half of its adenine into guanine. If it is offered 2:6-diaminopurine 

 at a non-inhibitory level, that is, about 2 /xg. of adenine per ml. (or 



