基因 Chapter 8 Protein Synthesis.pdf

Protein Synthesis Introduction • The rRNA of the 305 bacterial ribosomal subunit has a com­ plementary sequence that base pairs with the 5hine­ .. Protein Synthesis Occurs by Initiation, Elongation, Dalgarno sequence during initiation. ­ and Termination .­ Small Subunits Scan for Initiation Sites on Eukaryotic ~ • The ribosome has three tRNA-binding sites. mRNA • An aminoacyl-tRNA enters the A site. • Eukaryotic 405 ribosomal subunits bind to the 5 end of • Peptidyl-tRNA is bound in the P site. mRNA and scan the mRNA until they reach an initiation site. • Deacylated tRNA exits via the Esite. • A eukaryotic initiation site consists of a ten-nucleotide • An amino acid is added to the polypeptide chain by trans­ sequence that includes an AUG codon. ferring the polypeptide from peptidyl-tRNA in the P site to • 605 ribosomal subunits join the complex at the initiation aminoacyl-tRNA in the A site. site. Special Mechanisms Control the Accuracy of Protein Eukaryotes Use a Complex of Many Initiation Factors Synthesis