Selective inhibition of f2 RNA translation by sulfhydryl reagents

Escherichia coli ribosomes containing bound initiation factors were reacted with N-ethylmaleimide (NEM) under conditions where about 20 NEM molecules bind per ribosome. This treatment results in a large reduction in their ability to translate f2 RNA but not late T4 mRNA or polyuridylate. Iodoacetate produces a similar effect. These results indicate that ribosomal factors responsible for mRNA specificity differ appreciably in their sensitivity to inactivation by alkylation and suggest that translational control, dependent on mRNA selectivity, might operate by modifying the same or similar reactive sites.