Interactions between Membrane Functions and Protein Synthesis in Reticulocytes.

In this paper we demonstrate that two compounds which are known to enhance the permeability of membranes to potassium, valinomycin, a cyclic dodecapeptide and dicyclohexyl-18-crown-6, a macrocyclic polyether, inhibit protein synthesis in reticulocytes and that this inhibition is not primarily due to changes in the intracellular potassium concentration. No effect is obtained by adding the drugs to a cell free system and the inhibition observed is likely to be membrane mediated. Dicyclohexyl-18-crown-6 and low concentration of valinomycin (10 nM) act reversibly probably by interacting with the lipid phase of the membrane. This interaction in turn affects the protein synthesizing apparatus by affecting ribosomal functions. Ribosomes once isolated from treated cells are perfectly normal in structural and functional respects. High concentrations of valinomycin, which change the K+ gradient between the inside and the outside of the cell, affect the protein synthesizing apparatus of reticulocytes irreversibly by blocking incorporation of amino acids at the level of elongation or termination. Ribosomes isolated from cells treated with high valinomycin concentrations are mostly in the form of polysomes which are inactive in cell free protein synthesis. The high valinomycin block on the ribosomal fraction can be relieved either by washing ribosomes with high salt or with puromycin. It is believed that with high concentrations of valinomycin an inhibitor is released (probably from the membrane) and attached to the ribosomes. This high valinomycin effect is believed to by a supplementary phenomenon which when added to the effect of low valinomycin renders the inactivation of ribosomal functions irreversible.