Hybrid states model for the translational elongation cycle. Squares indicate A (aminoacyl), P (peptidyl), and E (exit) binding sites on the 50S and 30S ribosomal subunits. tRNAs are represented by vertical bars and the nascent polypeptide chain by a wavy line; aa represents the aminoacyl group and OH the deacylated 3' end of the tRNA; the circles represent elongation factors EF-Tu and EF-G; T signifies ternary complex. Binding states for tRNA are based on chemical footprinting studies; for example, A/P indicates interaction of the anticodon end of a tRNA with the 30S A site and its acceptor end to the 50S P site.
From: K. S. Wilson and H. F. Noller (1998) Molecular movement inside the translational engine. Cell 92: 337-349.