The Escherichia coli ribosomal proteins, L7/L12, are dominant over L11 in modulating the binding of RF-1 and RF-2 to ribosomes. The elevated activity of RF-2 on L11-lacking ribosomes over those containing L11 is abolished by IgG against L7/L12 or by removing the L7/L12 proteins. Adding back L7/L12 restores the original phenotype. The stimulatory factor, RF-3, is active on ribosomes depleted of L7/L12 but on those which lack L11 the stimulatory effects are less pronounced or often not seen. RF-3 cannot restore activity with RF-1 or RF-2 to ribosomes lacking both these sets of proteins. The stimulatory effects of an absence of either L11 or RF-3 on the activity of RF-2 are not additive or synergistic.
