37. NUCLEIC ACID AND PROTEIN SYNTHESIS 40") 



ume of (830 A 3 ) within a reticulocyte would contain twenty to thirty sRNA 

 molecules and one ribosome capable of producing one peptide bond per 

 second. Collision frequency estimates (based on an equation for coagulation 

 of colloids, as well as the kinetic theory of gases and Brownian movement) 

 lead to the conclusion that even if the collision efficiency were 0.1 % there 

 would be enough collisions to account for the rate of synthesis. 



Thus, we find that experimental observation is in good agreement with 

 the broad idea of an adaptor serving as an intermediate. However, there 

 are two matters which cause some perplexity. One is the fact that transfer 

 RNA is a larger molecule, by a factor of at least 10, than one would re- 

 quire on the basis. of current coding concepts. Perhaps these concepts are 

 totally wrong. It certainly seems difficult to conceive, however, of a reason 

 why such a large molecule should accompany each amino acid into the 

 particle. Perhaps a "coding piece" is split off the transfer RNA during the 

 transfer reaction and only this piece accompanies the amino acid into the 

 particle. The remainder of the molecule would only serve as a polymerized 

 carrier for the end group. An answer to this question can come from quanti- 

 tative studies on how much of the transfer RNA accompanies the amino 

 acid into the particles. These studies are in their infancy as we have seen 

 and do not give us a clear answer to this question. That acid soluble oligo- 

 nucleotides (possibly corresponding to fragments of transfer RNA) are 

 produced and consumed during the course of protein synthesis is suggested 

 by interesting observations of Gobert (cf. Chantrenne 186 ). It was found 

 that immediately after maltase induction into resting yeast cells the acid 

 soluble nucleotide pool rapidly increased, apparently by breakdown of ex- 

 isting RNA; and the increase was due chiefly to material tentatively identi- 

 fied as oligonucleotide in character. This was followed by a sharp fall in the 

 pool as new enzymes were synthesized. Such events might be indicative of 

 the release and subsequent consumption of coding fragments from transfer 

 RNA. Another experimental approach to this problem would be to look 

 for acid-soluble oligonucleotides with attached amino acids when transfer 

 RNA-amino acids are incubated with microsomes in the absence of GTP or 

 incubated in the presence of microsomes rendered incapable of incorpora- 

 tion for some other reason. Thus far, these experiments have shown that 

 oligonucleotide-like material is in fact enzymically produced from sRNA 

 by microsomes but it has not been possible to show that these fragments 

 contain amino acids, are able to bind amino acids, or are able to be used by 

 the ribosomes for protein synthesis. 233 



Perhaps the content of "pseudouridine" in sRNA has some significance 

 in such reactions. It has been suggested, also, that the high content of un- 

 usual bases might be an indication that the noncoding end of the molecule 



233 M. B. Hoagland, unpublished data, (1960). 



