STUDIES ON MECHANISM OF SYNTHESIS OF SOLUBLE RIBONUCLEIC ACID 1 23 



all four ribonucleoside 5 '-triphosphates resulted in almost complete re- 

 constitution of the capacity of this previously degraded S-RNA to accept 

 threonine (93% of the capacity of the control). 



We know that at least three of the four ribonucleotides can be incor- 

 porated into S-RNA (Table VII), and have presented evidence that all four 



TABLE VII 

 Effect of Phosphodiesterase on the Incorporation of ^*C-ATP, CTP, and 



UTP INTO S-RNA-/3 AND -y 



ribonucleotides are required to restore the amino acid-incorporating 

 capacity of the partly degraded S-RNA; we may therefore conclude that 

 whatever the type of reconstitution of the S-RNA that is occurring it is 

 not limited to the reconstitution of the terminal sequence — CMP — CMP — • 

 AMP but is more extensive. 



These experiments represent a first crude attempt to synthesize a 

 defined ribonucleotide sequence in a ribonucleic acid-complex, based on 

 the underlying a priori assumption that the ribonucleotide sequence of 

 the S-RNA determines the specificity of the amino acid attachment. The 

 results are unduly complicated bv the fact that we probablv do not have a 

 single species of S-RNA, but are at present using as a substrate a mixture 

 of ribonucleic acid molecules, as evidenced both by the ability of the 

 S-RNA to accept a variety of amino acids and by the results of the end- 

 group analysis. 



