Pactamycin (pactacin) is a unique type of highly-substituted aminocyclitol produced by Streptomyces sp. which is a potent inhibitor of translation in eukaryotes, bacteria and archaea, active against Gram positive and Gram negative bacteria. Pactamycin was patented by Upjohn Inc. in 1967 as an antiviral. Pactamycin binds to the 30S ribosomal subunit at a site distinct from tetracycline and hygromycin B, promoting structural changes that prevent the tRNA from binding. Pactamycin also exhibits antineoplastic and antimalarial properties. Although its use was limited by toxicity, some semisynthetic analogues are less toxic.