Deletion and insertion mutants in the structural gene for ribosomal protein S1 from Escherichia coli

Mutants have been constructed by deleting regions of the gene rpsA for ribosomal protein S1, which had been cloned in plasmid pACYC184. The mutant genes were analyzed for their ability to complement an S1 amber mutant containing a temperature-sensitive suppressor. Another series of mutants was constructed using the tac promoter plasmid pKK223-3, and the effect of the mutant proteins was analyzed in a strain wild type for rpsA. The gene products of all mutants were identified by the immunoblotting technique. Plasmids with a mutant rpsA gene which do not or only poorly complement the S1 amber mutation cause drastic growth reduction, whereas the overall protein synthesis is affected to different extents depending on the site of the deletion. Mutants which express S1 fragments comprising at least the NH2-terminal 100 amino acids stimulate or inhibit the synthesis of certain cellular proteins. The amount of chromosomal coded S1 was reduced by each mutant plasmid. Our data suggest that S1 has a general regulatory role during protein biosynthesis.