Enzymatic Modification of Proteins

Bovine thyroglobulin is an acceptor for arginine in the reaction catalyzed by arginyl-transfer RNA-protein transferase.The product formed with 14C-arginine has been shown to contain 2 eq of radioactive arginine per mole of thyroglobulin.The following evidence suggests that arginine is transferred to 2 NHz-terminal aspartic acid residues.First, the incorporated arginine was reactive with fluorodinitrobenzene; and second, the two principal radioactive peptides obtained after digestion with pepsin were isolated and their structures established as Arg-Asp-Ile-Phe and Arg-Asp, respectively.The data also indicate that bovine thyroglobulin contains at least one and possibly two chains which possess the NHzterminal sequence Asp-Ile-Phe-.