Tetracycline interferes with the attachment of tRNA carrying the amino acid to the mRNA-ribosome complex preventing the addition of amino acids to the growing polypeptide chain. Streptomycin interferes with the initial steps of protein synthesis by changing the shape of 30S proton of 70S prokaryotic ribosome. Erythromycin reacts with 50S portion of the 70S prokaryotic ribosome.