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Characterization of a plasmid-specified ribosome methylase associated with macrolide resistance

A G Shivakumar, D Dubnau

    Nucleic Acids Research
    |June 11, 1981
    PubMed

    Insights

    The ermC gene confers resistance to macrolide antibiotics by producing an RNA methylase enzyme. This enzyme

    Area of Science:

    • Molecular Biology
    • Microbiology
    • Antibiotic Resistance

    Background:

    • The ermC gene on plasmid pE194 confers resistance to macrolide, lincosamide, and streptogramin B antibiotics.
    • Erythromycin induces both ermC gene expression and the synthesis of its 29,000-dalton protein product.
    • Macrolide resistance is linked to adenine dimethylation in 23S ribosomal RNA (rRNA).

    Purpose of the Study:

    • To investigate the role of the ermC gene product in macrolide resistance.
    • To characterize the RNA methylase specified by the ermC gene.
    • To understand the induction mechanism of the methylase by erythromycin.

    Main Methods:

    • Enzyme assays using 50S ribosomes and 23S rRNA as substrates.
    • Polyacrylamide gel electrophoresis to analyze protein products.
    • Investigating gene expression under varying erythromycin concentrations.

    Main Results:

    • The pE194 plasmid encodes an RNA methylase that acts on 50S ribosomes and 23S rRNA.
    • Methylase synthesis is induced by low erythromycin concentrations.
    • High-copy number mutants of pE194 lead to increased methylase production.
    • The methylase comigrates with the 29K ermC protein on gels.

    Conclusions:

    • The ermC gene product is an RNA methylase responsible for erythromycin-induced macrolide resistance.
    • Erythromycin induction regulates the synthesis and expression of this key resistance enzyme.

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