Cloning and molecular characterization of the gene rimL which encodes an enzyme acetylating ribosomal protein L12 of Escherichia coli K12.

The rimL gene of Escherichia coli K12 encodes an enzyme catalyzing the acetylation of the N-terminal serine of ribosomal protein L12, thereby converting it into L7. Using a mutant strain defective in this acetylation reaction, we cloned the rimL gene into cosmid pHC79 and characterized it at the molecular level. From analysis by SDS-polyacrylamide gel electrophoresis of the proteins synthesized in maxi-cells containing derivatives of the rimL-harboring plasmid into which transposon gamma delta had been inserted at various sites, the product of this gene was identified as a protein with an apparent molecular weight of 20.3 kDa. The nucleotide sequence of the gene and the amino acid sequence deduced from the nucleotide sequence were compared with those of two other ribosomal protein acetylases encoded by the rimI and rimJ genes (Yoshikawa et al. 1987). A considerable degree of overall similarity was seen between rimL and rimJ, but the degree of similarity between rimL and rimI was very low. In addition, a short stretch of similar amino acid sequence was found in all three rim acetylases. The significance of these results with respect to other acetylating enzymes, in particular those involved in the acetylation of aminoglycoside antibiotics is discussed.