General Targets of Ribosome Decoding Center The decoding center (DC) is the region comprising the A site on the 30S subunit that monitors the correct base pairing between the mRNA codon and the anticodon of the aa-tRNA. This part of the ribosome consists of regions of the 30S head and shoulder, and the top of helix 44 (h44) of 16S rRNA. Antibiotics belonging to several different chemical classes bind in the DC, and some of them are used to treat a broad range of infections.