THE FUNCTION OF sRNA AS AMINO ACID ADAPTOR IN THE SYNTHESIS OF HEMOGLOBIN

According to the adaptor hypothesis of Crick [1] and Hoagland [2], the position of a particular amino acid in a polypeptide chain is determined, not by direct interaction between amino acid and template, but through the mediation of an sRNA molecule that functions as an adaptor. The hypothesis was tested by Chapeville et al. [3] in a cell-free protein-synthesizing system from E. coli, using a synthetic polynucleotide as template. Cysteine attached to sRNA was converted to alanine, forming an Ala-sRNACYSH hybrid (Fig. 1). The alanine was transferable into polypeptide in response to poly UG, which ordinarily stimulates the incorporation of cysteine but not of alanine. The present investigation shows that the result indicated by the use of the artificial messenger poly UG applies as well to the synthesis of hemoglobin, thus confirming the validity of the adaptor hypothesis in the synthesis of natural protein.