Autogenous control of the S10 ribosomal protein operon of Escherichia coli: genetic dissection of transcriptional and posttranscriptional regulation.

The S10 ribosomal protein operon is regulated autogenously by the product of one of the genes of the operon, the gene encoding ribosomal protein L4. We have used site-directed mutagenesis to isolate leader mutations affecting L4 control. The phenotypes of these mutants demonstrate that L4 regulates both transcription and translation of the S10 operon. Several mutations abolish both levels of L4 control; others eliminate either transcriptional or translational control with little or no effect on the other mode of regulation. We conclude that L4-mediated transcriptional and translational control share some sequence requirements, but the two regulatory processes recognize somewhat different features of the S10 leader. Primary as well as secondary structures within the S10 leader appear to be involved.