Tetracycline

Originally isolated from Streptomyces aureofaciens in 1948, there are now many tetracycline derivatives available. They bind to a single site on the 30S ribosomal subunit to block the attachment of aminoacyl tRNA to the acceptor site and thus inhibit protein synthesis (19). Tetracycline resistance is conferred by efflux proteins, TetA (A-E), which catalyze the energy-dependent export of tetracycline from the cell against a concentration gradient (19).