On the control of ribosomal protein biosynthesis in E. coli

E. coli strain RH 2859 carrying a mutation in rplX gene (Cabezon, 1977) does not assemble 50S subunits when grown at non-permissive temperature, while the assembly of functional 30S subunits proceeds normally. Abortive 30-32S particles, containing 23S RNA or its precursor form and a certain number of 50S proteins, accumulate. Protein analysis of those particles indicates that several 50S proteins are either missing or present in reduced amount (L7/12, L20, L24, L26, L27, L28, L32 and L33). Also newly synthesized 50 S proteins appear to exchange with preformed 50S subunits.