Elongation factor explained
Elongation factor should not be confused with Relative elongation.
Elongation factors are a set of proteins that function at the ribosome, during protein synthesis, to facilitate translational elongation from the formation of the first to the last peptide bond of a growing polypeptide. Most common elongation factors in prokaryotes are EF-Tu, EF-Ts, EF-G.[1] Bacteria and eukaryotes use elongation factors that are largely homologous to each other, but with distinct structures and different research nomenclatures.[2]
Elongation is the most rapid step in translation.[3] In bacteria, it proceeds at a rate of 15 to 20 amino acids added per second (about 45-60 nucleotides per second). In eukaryotes the rate is about two amino acids per second (about 6 nucleotides read per second). Elongation factors play a role in orchestrating the events of this process, and in ensuring the high accuracy translation at these speeds.
Nomenclature of homologous EFs
Elongation factors| Bacterial | Eukaryotic/Archaeal | Function |
|---|
| eEF-1A (α) | mediates the entry of the aminoacyl tRNA into a free site of the ribosome.[4] |
| eEF-1B (βγ) | serves as the guanine nucleotide exchange factor for EF-Tu, catalyzing the release of GDP from EF-Tu. |
| | catalyzes the translocation of the tRNA and mRNA down the ribosome at the end of each round of polypeptide elongation. Causes large conformation changes.[5] |
| | possibly stimulates formation of peptide bonds and resolves stalls.[6] |
| (None) | Proofreading |
| Note that EIF5A, the archaeal and eukaryotic homolog to EF-P, was named as an initiation factor but now considered an elongation factor as well. | |
In addition to their cytoplasmic machinery, eukaryotic mitochondria and plastids have their own translation machinery, each with their own set of bacterial-type elongation factors.[7] [8] In humans, they include TUFM, TSFM, GFM1, GFM2, GUF1; the nominal release factor MTRFR may also play a role in elongation.[9]
In bacteria, selenocysteinyl-tRNA requires a special elongation factor SelB related to EF-Tu. A few homologs are also found in archaea, but the functions are unknown.[10]
As a target
Elongation factors are targets for the toxins of some pathogens. For instance, Corynebacterium diphtheriae produces diphtheria toxin, which alters protein function in the host by inactivating elongation factor (EF-2). This results in the pathology and symptoms associated with diphtheria. Likewise, Pseudomonas aeruginosa exotoxin A inactivates EF-2.[11]
Further reading
- Alberts, B. et al. (2002). Molecular Biology of the Cell, 4th ed. New York: Garland Science. .
- Berg, J. M. et al. (2002). Biochemistry, 5th ed. New York: W.H. Freeman and Company. .
- Singh, B. D. (2002). Fundamentals of Genetics, New Delhi, India: Kalyani Publishers. .
External links
- nobelprize.org Explaining the function of eukaryotic elongation factors
Notes and References
- Encyclopedia: Parker . J. . Elongation Factors; Translation . Encyclopedia of Genetics . 2001 . 610–611 . 10.1006/rwgn.2001.0402. 9780122270802 .
- Sasikumar. Arjun N.. Perez. Winder B.. Kinzy. Terri Goss. July 2012. The Many Roles of the Eukaryotic Elongation Factor 1 Complex. Wiley Interdisciplinary Reviews. RNA. 3. 4. 543–555. 10.1002/wrna.1118. 1757-7004. 3374885. 22555874.
- Prabhakar. Arjun. Choi. Junhong. Wang. Jinfan. Petrov. Alexey. Puglisi. Joseph D.. July 2017. Dynamic basis of fidelity and speed in translation: Coordinated multistep mechanisms of elongation and termination. Protein Science . 26. 7. 1352–1362. 10.1002/pro.3190. 0961-8368. 5477533. 28480640.
- Weijland A, Harmark K, Cool RH, Anborgh PH, Parmeggiani A . Elongation factor Tu: a molecular switch in protein biosynthesis . Molecular Microbiology . 6 . 6 . 683–8 . March 1992 . 1573997 . 10.1111/j.1365-2958.1992.tb01516.x . free .
- Jørgensen . R . Ortiz . PA . Carr-Schmid . A . Nissen . P . Kinzy . TG . Andersen . GR . Two crystal structures demonstrate large conformational changes in the eukaryotic ribosomal translocase. . Nature Structural Biology . May 2003 . 10 . 5 . 379–85 . 10.1038/nsb923 . 12692531. 4795260 .
- Rossi . D . Kuroshu . R . Zanelli . CF . Valentini . SR . eIF5A and EF-P: two unique translation factors are now traveling the same road. . Wiley Interdisciplinary Reviews. RNA . 2013 . 5 . 2 . 209–22 . 10.1002/wrna.1211 . 24402910. 25447826 .
- free . Manuell . Andrea L . Quispe . Joel . Mayfield . Stephen P . Petsko . Gregory A . Structure of the Chloroplast Ribosome: Novel Domains for Translation Regulation . PLOS Biology . 7 August 2007 . 5 . 8 . e209 . 10.1371/journal.pbio.0050209. 17683199 . 1939882 .
- G C Atkinson . S L Baldauf . Evolution of elongation factor G and the origins of mitochondrial and chloroplast forms. Molecular Biology and Evolution. 2011. 28. 3. 1281–92. 21097998. 10.1093/molbev/msq316 . free.
- Web site: KEGG DISEASE: Combined oxidative phosphorylation deficiency . www.genome.jp.
- Atkinson . Gemma C . Hauryliuk . Vasili . Tenson . Tanel . An ancient family of SelB elongation factor-like proteins with a broad but disjunct distribution across archaea . BMC Evolutionary Biology . 21 January 2011 . 11 . 1 . 22 . 10.1186/1471-2148-11-22. 21255425 . 3037878 . free .
- Lee H, Iglewski WJ . 1984 . Cellular ADP-ribosyltransferase with the same mechanism of action as diphtheria toxin and Pseudomonas toxin A . Proc. Natl. Acad. Sci. U.S.A. . 81 . 2703 - 7 . 6326138 . 10.1073/pnas.81.9.2703 . 9 . 345138 . 1984PNAS...81.2703L . free .
