Figure 1.

Schematic diagram of bacterial protein synthesis. Shown are the main steps comprising the translation process: initiation, elongation cycle, termination and recycling. (The elongation cycle is started with the complex marked with* — at this point only it is called an initiation complex and has the initiator tRNA in the P site and an empty E site. In subsequent iterations of the cycle this complex has an ordinary tRNA in the P site and has the E site occupied.) Details regarding each step are provided in the main text. For simplicity, some intermediate stages are omitted in this overview. The mRNA is depicted as a strand running horizontally along the small (30S) subunit, with alternating white and black segments, each representing one codon. The tRNAs bind at A, P and E sites. The nascent polypeptide is shown as a string of spheres. The individual structures and cartoons are not drawn to scale.