Elongation factor

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EF-Tu with tRNA[1]

Elongation factors are a set of proteins that are used in protein synthesis in the process of cell cycle and elongation in some cells. In the ribosome, they facilitate translational elongation, from the formation of the first peptide bond to the formation of the last one. Bacteria and eukaryotes use elongation factors that are largely homologous to each other, but with a different nomenclature.

Elongation is the most rapid step in translation:

  • 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.

Elongation factors play a role in orchestrating the events of this process, and in ensuring the 99.99% accuracy of translation at this speed.

Elongation factors
Bacterial Eukaryotic/Archaeal Function
EF-Tu eEF-1 subunit α mediates the entry of the aminoacyl tRNA into a free site of the ribosome
EF-Ts eEF-1 subunit βγ serves as the guanine nucleotide exchange factor for EF-Tu, catalyzing the release of GDP from EF-Tu.
EF-G eEF-2 catalyzes the translocation of the tRNA and mRNA down the ribosome at the end of each round of polypeptide elongation. Shaped like EF-Tu plus tRNA.
EF-P EIF5A stimulates peptide formation by catalyzing the first synthesis step between the first amino acid (N-formylmethionine/methionine) and the second amino acid.
Note that EIF5A, the archaeal and eukaryotic homolog to EF-P, is instead considered an initiation factor.

In addition to their cytoplasmic machinery, eukaryotic mitochrondria and plastids have their own translation machineries with their own set of bacterial-type elongation factors. In humans, they include TUFM, TSFM, GFM1, GFM2.

As a target[edit]

Elongation factors are also a target for pathogen toxins. Corynebacterium diphtheriae produces the diphtheria toxin that alters protein function in the host by inactivating elongation factor (EF-2). This causes pharyngitis and pseudomembranous inflammation in the throat.

Pseudomonas aeruginosa's exotoxin A also inhibits EF-2.

References[edit]

  1. ^ PDB Molecule of the Month Elongation factors - September 2006
  • Alberts, B. et al. (2002). Molecular Biology of the Cell, 4th ed. New York: Garland Science. ISBN 0-8153-3218-1
  • Berg, J. M. et al. (2002). Biochemistry, 5th ed. New York: W.H. Freeman and Company. ISBN 0-7167-3051-0
  • Singh, B. D. (2002). Fundamentals of Genetics, New Delhi, India: Kalyani Publishers. ISBN 81-7663-109-4

External links[edit]