Action of spleen exonuclease on transfer ribonucleic acid.

The hydrolytic action of spleen exonuclease on serine transfer RNA has been investigated. It was found that two different mechanisms of attack obtain: (a) processive degradation and (b) random cleavage. These two diiferent modes of action are determined by the presence or the absence of the terminal phosphate group at the 5’ terminus of transfer RNA. The loss of several important biological activities of transfer RNA or aminoacyl transfer RNA, such as amino acid acceptor activity, AMP acceptor activity, polynucleotidedirected ribosomal binding, and incorporation of the amino acid moiety into growing polypeptide chains, were examined in detail as a function of the digestion by spleen exonuclease.