411 Protein Biosynthesis

initiation

• Binding: The small subunit binds to the Shine-Dalgarno sequence

• Initiator tRNA docking: tRNA-fMet binds to the start codon in the P-site.

• Initiation complex: The large subunit binds with the tRNA-fMet in the P-

site and forms the complete ribosome

elongation

• Binding of aminoacyl-tRNA: The next charged tRNA binds to the codon in

the A-site

• Peptide bond formation: The ribosome catalyzes the formation of the

peptide bond, transferring the peptide chain in the P site onto the amino

acid in the A site.

• Translocation: The ribosome shifts down the mRNA (translocation).

• The uncharged tRNA is moved to the E-site, and the new peptide-

carrying tRNA is moved to the P-site.

• The uncharged tRNA is ejected from the E-site.

• This is repeated until a stop codon is encountered.

termination

• When a stop codon is translocated to the A-site, translation pauses.

• The release factors recognize the stop codon and terminate protein

synthesis.

• Ribosome disassembly: the ribosome dissociates from the mRNA

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