MUTATIONS IN THE RPMBG OPERON OF ESCHERICHIA-COLI THAT AFFECT RIBOSOME ASSEMBLY

The rpmBG operon of Escherichia coli codes for ribosomal proteins L28 and L33. Two strains with mutations in the operon are AM81, whose ribo somes lack protein L28, and AM90, whose ribosomes are without protein L33, Neither strain showed major defects in ribosome assembly, However , when the mutations were transferred to other strains of E. coli, rib osome synthesis was greatly perturbed and precursor ribonucleoproteins accumulated, In the new backgrounds, the mutation in rpmB was complem ented by synthesis of protein L28 from a plasmid; the rpmG mutation wa s not complemented by protein L33 because synthesis of protein L28 fro m the upstream rpmB gene was also greatly reduced, The results suggest that protein L33, in contrast to protein L28, has at best a minor rol e in ribosome assembly and function.