Seryl Transfer Ribonucleic Acid Synthetase from Bakers' Yeast

Seryl transfer RNA synthetase from bakers' yeast reacted with adenosine triphosphate and serine in the presence of magnesium to form a seryladenylate-enzyme complex which could transfer its seryl moiety to serine tRNA from yeast only in the presence of magnesium or other suitable cofactor. Spermidine was an effective substitute for magnesium in the transfer reaction. Serine-specific tRNA from yeast had a marked labilizing effect on the seryladenylate-enzyme complex to a greater extent than could be accounted for by the degree of transfer. Non-amino acid-accepting CpC terminal serine tRNA from yeast also had this property, but serine tRNA from Escherichia coli and a mixture of non-serine tRNAs from yeast did not.