Sulfur: incorporation into the transfer fraction of soluble ribonucleic acid.

When S(35)-labeled soluble RNA from Escherichia coli K 38 is subjected to gel filtration, four fractions of RNA are obtained by elution. Only one RNA fraction, the transfer RNA, contains sulfur, presumably as thionucleotides. Treatment with ribonuclease suggests that the incorporated sulfur is an integral part of the polynucleotide chain; digestion with alkali yields a mixture of products containing sulfur, the major one being eluted in a position similar to uridine diphosphate upon Dowex-l chromatography. Analysis by countercurrent distribution of S(35)-labeledtransfer RNA from E. coli B reveals that the incorporated sulfur is found in many RNA's that accept amino acids, but the possibility remains that not all acceptor RNA's contain sulfur.