Micrococcin: Acceptor‐Site‐Specific Inhibitor of Protein Synthesis

Micrococcin inhibited the binding of aminoacyl‐tRNA at 13 mM Mg 2+ , but not at 6 mM Mg 2+ . The elongation factor Tu (EF‐Tu)‐dependent binding of aminoacyl‐tRNA was inhibited appreciably by 7 μM micrococcin. The EF‐G‐dependent puromycin reaction of the ribosome‐bound aminoacyl‐tRNA, release of unesterified tRNA concomitant with translocation, and the EF‐G‐dependent evacuation of aminoacyl‐tRNA from the acceptor site of the ribosomes were all sensitive to this antibiotic. It is concluded that micrococcin interacts with the acceptor site specifically and this interaction results in the dual action of this antibiotic, namely inhibition of translocation and the binding of aminoacyl‐tRNA.