Cloning and DNA sequence determination of the L11 ribosomal protein operon of Serratia marcescens and Proteus vulgaris: translational feedback regulation of the Escherichia coli L11 operon by heterologous L1 proteins.

In Escherichia coli the genes encoding ribosomal proteins L11 (rplK) and L1 (rplA) are contained in a single operon and their expression is translationally regulated by L1. We have cloned the homologous genes from two other enterobacteria, Serratia marcescens and Proteus vulgaris, and determined nucleotide sequences. The genes are organized in a similar way to that found in E. coli. Conservation of nucleotide and amino acid sequences relative to E. coli in the protein coding regions are 89.2% and 94.7% for S. marcescens, and 80.9% and 88.6% for P. vulgaris. Nucleotide sequences of L11 mRNA leader regions were strongly conserved for the primary as well as the secondary structures in the L1 target site. We have also constructed plasmids carrying E. coli L11 and either P. vulgaris or S. marcescens L1 genes fused to the lac promoter, with or without the E. coli leader containing the L1 target site. Induction of transcription of the operons possessing the E. coli mRNA leader did not lead to overproduction of L11, indicating translational regulation of the chimeric operon as well as the chromosomal operon by the plasmid encoded L1. Repression of the chromosomal L11 operon was directly demonstrated upon induction of the chimeric operons without the leader, which also lack the L11 initiation signal but have a mutation allowing L1 translation.(ABSTRACT TRUNCATED AT 250 WORDS)