Josamycin solution, 10 µg/ml in acetonitrile

Josamycin is a member of the leucomycin family of macrolide antibiotics produced by Streptomyces kitasatoensis. It is an antimicrobial against a wide variety of pathogens. It has activity against Gram-positive an Gram-negative bacteria. The mechanism of action is via inhibition of bacterial protein biosynthesis by binding reversibly to the subunit 50S of the bacterial ribosome, inhibiting peptidyltransferase and ribosomal translocation, thereby inhibiting translocation of peptidyl tRNA. Josamycin may overcome anticancer drug resistance by inhibiting the binding of vinblastine or cyclosporin A to P-glycoprotein (Pgp). It is used to study the modification of phagocytosis and cytokine production by macrolide antibiotics and immunomodulatory effects.