Viomycin

Viomycin is a cyclic polypeptide antibiotic isolated from *Streptomyces puniceus* that serves as an antimicrobial agent rather than a therapeutic target. It functions by binding to bacterial ribosomes at the interface between the small and large ribosomal subunits, where it stabilizes transfer RNA in the A site and prevents ribosomal translocation, thereby inhibiting bacterial protein synthesis. This mechanism of action makes it particularly valuable for treating tuberculosis and multidrug-resistant forms of the disease. The antibiotic has also played a pivotal role in biochemical research on protein synthesis mechanisms. While effective against bacterial pathogens, viomycin exhibits hemolytic activity in vitro, which represents a notable safety consideration for therapeutic use.

Other names

Vinacetin AViomicinaViomycineViomycinum

Viomycin acts by blocking bacterial ribosomal translocation. Specifically, viomycin binds to the ribosome at the interface between helix 44 of the small ribosomal subunit and helix 69 of the large ribosomal subunit. The drug stabilizes tRNA in the A site in the pretranslocation state, preventing translocation of tRNA molecules during protein synthesis. Although viomycin allows binding of elongation factor G (EF-G) and GTP hydrolysis, it completely inhibits the translocation step, effectively inhibiting protein synthesis in bacterial cells. Additionally, viomycin increases the affinity of tRNA to the A site by approximately 1000-fold and promotes back translocation of the tRNA-mRNA complex.