Figure 1

Conformational changes in release factors and the ribosomal decoding centre. Release factor conformations are shown in (A) absence of the ribosome (from PDB entry 2IHR [10]), (B) bound to the ribosome containing a UAA stop codon (from PDB entry 3D5A [7]). The catalytic domain 3 is indicated in blue, the stop codon recognition domain (consisting of domains 2 and 4) is shown in orange and domain 1 is colored red. The switch loop is highlighted in green. The conformation of the universally conserved ribosome decoding site nucleotides A-1492 and A-1493 is shown (C) in case of an empty A-site with both bases stacked (from PDB entry 1J5E [11]), (D) with mRNA and a cognate tRNA present in the A-site and both bases unstacked (from PDB entry 1IBM [12]) and (E) with a stop codon and a release factor present in the A-site in an intermediate state (from PDB entry 3MR8 [8]). The mRNA present in the A-site is shown in green in panel D (UUU) and panel E (UAA), the conserved decoding centre in cyan. The tRNA molecule (panel D) and release factor molecule (panel E) have been omitted for clarity.