Английская Википедия:Elongation factor
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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).Шаблон:Citation needed In eukaryotes the rate is about two amino acids per second (about 6 nucleotides read per second).Шаблон:Citation needed Elongation factors play a role in orchestrating the events of this process, and in ensuring the high accuracy translation at these speeds.Шаблон:Citation needed
Nomenclature of homologous EFs
| Bacterial | Eukaryotic/Archaeal | Function |
|---|---|---|
| EF-Tu | eEF-1A (α)[2] | mediates the entry of the aminoacyl tRNA into a free site of the ribosome.[4] |
| EF-Ts | eEF-1B (βγ)[2] | serves as the guanine nucleotide exchange factor for EF-Tu, catalyzing the release of GDP from EF-Tu.[2] |
| EF-G | eEF-2 | 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] |
| EF-P | eIF-5A | possibly stimulates formation of peptide bonds and resolves stalls.[6] |
| EF-4 | (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.[6] | ||
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 (Шаблон:UniProt) 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]
References
Further reading
- Alberts, B. et al. (2002). Molecular Biology of the Cell, 4th ed. New York: Garland Science. Шаблон:ISBN.Шаблон:Page needed
- Berg, J. M. et al. (2002). Biochemistry, 5th ed. New York: W.H. Freeman and Company. Шаблон:ISBN.Шаблон:Page needed
- Singh, B. D. (2002). Fundamentals of Genetics, New Delhi, India: Kalyani Publishers. Шаблон:ISBN.Шаблон:Page needed
External links
- nobelprize.org Explaining the function of eukaryotic elongation factors
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