Cooperative control of translational fidelity by ribosomal proteins in Escherichia coli. III. A ram mutation in the structural gene for protein S5 (rpx E).

The effect on translational fidelity of a particular mutation in the gene coding for protein S5(rpxE) has been investigated. This mutation has the opposite effect of a restrictive strA mutation; in vivo, it relieves the restriction imposed by strA on the suppression of T4 nonsense mutants and results in hypersensitivity to streptomycin; in vitro, the presence of the altered S5 protein in 30S ribosomes results in increased intrinsic misreading. It is concluded that this mutation, ramC319, acts as a ribosomal ambiguity mutation similar to certain mutations of protein S4 (ramA).