Tracing of the In Vivo Path from Amino Acid to Protein

Abstract
Experimental evidence is presented to support the concept that in in vivo protein synthesis, each amino acid is activated through formation of an anhydride-type com-pound with a phosphate, in which the amino acid carboxyl forms the bridge oxygen between the acyl carbon and the phosphorus. Apparently these reactions are localized within the cell and no interchange of the phosphate compounds in this localized area occurs with other intracellular phosphate or with the inorganic phosphate of the medium.