P(peptidyl)site A(aminoacyl)site 50S subunit E(exit)site mRNA-binding site 30S subunit (a) A site P site E site 50S Growing peptide chain mRNA-binding site 30S 031 mRNA (b) Figure 20-2 Important Binding Sites on the Prokaryotic Ribosome. 主讲：汤华主讲：汤 华