Figure 1.

Pathway of protein synthesis in bacteria. The simplified cartoon shows the four phases of protein synthesis and how the ribosomes, tRNAs, mRNA, and GTP interact. Not shown are the initiation, elongation, and termination factors that promote the reactions. Following initiation, each turn of the elongation cycle results in the addition of another amino acid (gray pentagon) to the growing peptide chain (not shown). Termination occurs when a termination codon (UAA, UAG, UGA) appears in the ribosomal A-site and involves hydrolysis of the peptidy-tRNA in the P-site. (Figure constructed by Nancy Villa, University of California, Davis.)