Pactamycin is a naturally occuring antibiotic produced by Streptomyces pactum and used as an anticancer agent. It acts as a potent protein synthesis inhibitor, inhibiting protein synthesis at the translocation step on the 70S ribosome. It has activity against Gram-positive and Gram-negative bacteria, and broad antitumor, antiviral, and antiplasmodial activity. Cytotoxicity limits it clinical use. It is also used as a tool in biochemistry because it inhibits certain steps in protein synthesis.