Specific inhibition of peptide-chain initiation by 2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide.

Abstract

M DMP (2-(4-methyl-2,6-dinitroanilino)-N-methyl- propionamide) is a potent inhibitor of mRNA-dependent amino acid incorporation in the in citro wheat embryo amino acid incorporating system. At concentrations above 5 X lo-,) hi, TMV-RNA-directed peptide synthesis is inhibited more than 957& Amino acid incorporation by polyribo- bomes (obtained from germinating wheat embryos) is not affected by MDMP. Similarly, polyuridylic acid directed polyphenylalanine synthesis is not affected by MDMP. These data indicate that MDMP inhibits peptide-chain initiation and does not affect peptide chain elongation. More precise localization of the MDMP inhibition is obtained by studying the effect of the inhibitor on the initiation reactions involved M uch progress has been made in elucidating the scheme of protein chain initiation in eukaryotic organisms. The over- all sequence of mRNA, initiator Met-tRNA and ribosomal subunit involvement has been clearly defined (Crystal et al., 1971; Prichard et al., 1971; Heywood and Thompson, 1971; Pragnell et al., 1971 ; Hoerz and McCarty, 1971 ; Burgess and Mach, 1971 ; Weeks et al., 1972) while the isolation and char- acterization of specific factors required for the constitutive reactions are well advanced (Crystal et a/., 1971 ; Heywood and Thompson, 1971 ; Seal et a/., 1972). Detailed anaylses of the individual partial reactions of initiation can be greatly facilitated by the availability of inhibitors with strict speci- ficity, such as those which have been used to great advantage in delineating the partial reactions of procaryotic protein synthesis (Pestka, 1971). Presently, however, the number of inhibitors available which specifically interfere with known steps of eukaryotic peptide-chain initiation is quite limited (i.e., aurintricarboxylic acid (Stewart et al., 1971 ; Marcus et a/., 1970a), edeine (Obrig et al., 1971), NaF (Hoerz and McCarty, 1971), and pactamycin (MacDonald and Gold- berg, 1970; Seal and Marcus, 1972)l. We now report a new inhibitor of eukaryotic peptide-chain initiation, 2-(4-methyl-