Functional insights from the structure of the 30S ribosomal subunit and its interactions with antibiotics

The 30S ribosomal subunit has two primary functions in protein synthesis. I t discriminates against aminoacyl transfer RNAs that do not match the codon of messenger RNA, thereby ensuring accuracy in translation of the genetic message in a process called decoding. Also, it works with the 50S subunit t o move the tRNAs and associated mRNA by precisely one codon, in a process c alled translocation. Here we describe the functional implications of the hi gh-resolution 30S crystal structure presented in the accompanying paper, an d infer details of the interactions between the 30S subunit and its tRNA an d mRNA ligands. We also describe the crystal structure of the 30S subunit c omplexed with the antibiotics paromomycin, streptomycin and spectinomycin, which interfere with decoding and translocation. This work reveals the stru ctural basis for the action of these antibiotics, and leads to a model for the role of the universally conserved 16S RNA residues A1492 and A1493 in t he decoding process.