Protein Synthesis Termination


Protein synthesis termination is the process by which a completed polypeptide is released from the ribosome after the coding information within a messenger ribonucleic acid (mRNA) has been successfully translated.

Keywords: termination signal; release factor; ribosome recycling factor; completed polypeptide; recoding

Figure 1.

Major components of the termination reaction: the aminoacyl‐tRNA in the ribosomal P‐site with the attached completed polypeptide; the class I RF in the A‐site with the associated class II RF; and the mRNA threaded through the ribosome past the decoding site. A, P and E are ribosome binding sites for tRNAs and are part of the active centre of the ribosome.

Figure 2.

Interactions of the class I RF with other participants in the termination complex are represented by lines. The class I RF decodes the stop codon (in this case UAA) in the mRNA and makes contact with the next three bases downstream. Probable interactions are also shown between the RF and the ribosome, the last tRNA, and the last two amino acids of the polypeptide.

Figure 3.

Cartoons of the structures of functional complexes of EF‐G and EF‐Tu and the putative structure of the functional complex of the class I and class II RFs based on sequence similarity. RF3 has sequence homology with EF‐G domains G, G′, II and III, and domains III, IV and V of EF‐G mimic the structure of a tRNA. Class I RFs have functional similarity with tRNA.

Figure 4.

+1 Frameshift at the RF2 recoding site. The AGG GGG in the mRNA interacts with the ribosomal RNA. The CUU at codon position 25 is a ‘slippery’ codon where the slippage of the reading frame occurs. UGACUA is a weak stop signal, which favours a frameshift into the +1 frame at the site, rather than efficient termination of protein synthesis. The amino acid sequence in the new frame is shown below.


Further Reading

Buckingham RH, Grentzmann G and Kisselev L (1997) Polypeptide chain release factors. Molecular Microbiology 24: 449–456.

Dalphin ME, Brown CM, Stockwell PA and Tate WP (1997) The translational signal database, TransTerm: more organisms, complete genomes. Nucleic Acids Research 25: 246–247.

Janosi L, Hara H, Zhang S and Kaji A (1996) Ribosome recycling by ribosome recycling factor (RRF) – an important but overlooked step of protein biosynthesis. Advances in Biophysics 32: 121–201.

Nakamura Y, Ito K and Isaksson LA (1996) Emerging understanding of translation termination. Cell 78: 147–150.

Tate WP and Brown CM (1992) Translational termination: ‘Stop’ for protein synthesis or ‘pause’ for regulation of gene expression. Biochemistry 31: 2443–2450.

Tate WP and Mannering SA (1996) Three, four or more: the translational stop signal at length. Molecular Microbiology 21: 213–219.

Tate WP, Poole ES and Mannering SA (1996) Hidden infidelities of the translational stop signal. Progress in Nucleic Acid Research and Molecular Biology 52: 293–335.

TransTerm‐97 [] [A database of translational signals including initiation and termination contexts]

Tuite MF and Stansfield I (1994) Termination of protein synthesis. Molecular Biology Reports 19: 171–181.

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Tate, Warren P, Poole, Elizabeth S, and Mannering, Sally A(Apr 2001) Protein Synthesis Termination. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0000549]