124 CYTOCHEMISTRY OF PROTEINS 



between protein and pentose nucleic acid is itself controlled by 

 the concentration of histone: since histones are more basic 

 than most proteins, histone will compete for nucleic acid more 

 successfully than most proteins. Hence an increase in histone 

 will cut down protein synthesis, and an increase in pentose nucleic 

 acid will enhance protein synthesis. 



The work of Caspersson and Brachet and their colleagues ap- 

 pears to be compatible with this scheme. It is interesting to ob- 

 serve that Stedman and Stedman (1943) found that the concen- 

 tration of histone is lowest in rapidly growing tissues such as 

 tumours and embryos, as is required by this theory. Correspond- 

 ingly, in red cells, which have a very high histone content, growth 

 has practically ceased. 



If this scheme were correct one would predict that, since pro- 

 tamine is a more basic protein than histone, it should be a more 

 efficient competitor for nucleic acid than is histone, and so should 

 be a strong inhibitor of protein synthesis. That is, synthesis 

 should be very low in cells containing a high protamine content; 

 this is certainly the case with spermatozoa. 



We thus have two distinctly possible roles for nucleic acids in 

 protein synthesis, neither of which involves direct participation 

 in formation of polypeptide chains. These two theories seem to 

 me to be equally possible, and the fact that this is so makes it 

 plain that much more information is required. But it must be 

 noted that it is not impossible that both theories may be cor- 

 rect, i.e., that nucleic acids may act both as trapping and as fold- 

 ing agents. One possibility would be that deoxynucleic acid acts 

 mainly as a folding agent, and pentose nucleic acid mainly as a 

 trapping agent. 



REFERENCES 



Avery, McLeod, and McCarty. 1944. J. Exp. Med., 79, 137. 

 Brachet. 1940. C. r. soc. biol, 133, 90. 

 Barron. 1949. Personal Communication. 

 Caspersson. 1947. Symp. Soc. Exp. Biol, 1, 127. 



1950. Cell Growth and Cell Function (Norton, New York). 

 Caspersson and Schultz. 1938. Nature, 122, 294. 



1939. Arch. exp. Zellforsch., 22, 650. 

 Cohen. 1949. Bact. Rev., 13, 1. 

 Danielli. 1946a. Nature, 157, 755. 



19466. J. Exp. Biol, 22, 110. 



1949. Cold Spring Harbor Symposia, 14, 32. 



