Variations in phenotype of relB mutants of Escherichia coli and the effect of pus and sup mutations.

Three independent relB mutants were studied. During amino acid starvation they all accumulate RNA and produce an inhibitor of in vitro protein synthesis; after starvation growth is retarded for hours. The mutants differ in the degree to which the common phenotype is expressed, but the characteristic thermolability of the inhibitor is the same. The phenotype of the relB mutants is accentuated by amber suppressors, and this effect is counteracted by a mutation, pus-1 that maps at 19.5 min near aroA.