RIBOSOME ASSEMBLY IN 3 STRAINS OF ESCHERICHIA-COLI WITH MUTATIONS IN THE RPMB,G OPERON

The rpmB,G operon of Escherichia coli codes for the synthesis of ribos omal proteins L28 and L33. In one mutant strain (TP28), these two prot eins are made at about half their normal rates, ribosome assembly is g reatly perturbed and precursor particles accumulate. The mutation in s train TP28 is in a Shine-Dalgarno sequence in the leader region of the rpmB,G messenger RNA. Another mutant, strain AM108, makes neither pro tein because it has the mobile element IS1 inserted into the rpmB codi ng sequence. Surprisingly, ribosome assembly in this strain is virtual ly normal with respect to growth rate. Strain AM90, which fails to mak e protein L33, has the element IS3 inserted into rpmG and also shows n o major defects in ribosome assembly.