Pyrocatechol violet: An inhibitor of initiation of protein synthesis

Pyrocatechol violet inhibits synthesis of globin in reticulocyte lysates at concentrations between 0.01 – 1 mM. After adding the dye, there is a delay of two minutes before inhibition is observed. Pyrocatechol violet induces sequential breakdown of polyribosomes to single ribosomes and ribosomal subunits; concomitantly, nascent peptides are released from the ribosomes as completed chains of globin. These observations suggest that the principal inhibitory effect of the dye is on initiation of protein synthesis. Pyrocatechol violet is as active as aurintricar?ylic acid in this respect but is more selective in its inhibitory action. The dye also prevents binding of 3H-poly U to reticulocyte ribosomes but does not affect binding of uncharged transfer RNA to the ribosome.