Niddamycin, a macrolide antibiotic, binds 50S ribosomal subunits to inhibit protein synthesis[1].
References
[1] S J Kakavas, et al. Identification and characterization of the niddamycin polyketide synthase genes from Streptomyces caelestis. J Bacteriol. 1997 Dec;179(23):7515-22. DOI:10.1128/jb.179.23.7515-7522.1997