mRNA bound to the 30S ribosomal subunit. (A) A 36-nucleotide mRNA is bound to the 30S ribosomal subunit. rRNA is shown in grey, mRNA is shown in yellow, and protein is shown in cyan. The ASD sequence of the 16S rRNA is shown in red to indicate the SD-ASD interaction. The P-site initiation codon is shown in green, and the A-site codon is shown in magenta. Note the kink in the mRNA between the two codons. (B) Close-up of the region indicated in panel A. The upstream and downstream tunnels are marked by arrows. Colors are the same as in panel A. The structure is derived from PDB entry 1JGQ, prepared using the program Ribbons (25), and rendered in Pov-Ray.