EEF-1


eEF-1 are two eukaryotic elongation factors. It forms two complexes, the EF-Tu homolog EF-1A and the EF-Ts homolog EF-1B, the former's guanide exchange factor. Both are also found in archaea.

Structure

The nomenclature for the eEF-1 subunits have somewhat shifted around circa 2001, as it was recognized that the EF-1A and EF-1B complexes are to some extent independent of each other. Components as currently recognized and named include:
Current NomenclatureOld NomenclatureHuman GenesCanonical Function
eEF1AeEF1AEEF1A1, EEF1A2
EEF1A1P43		aa-tRNA delivery to the ribosome
eEF1Bα
eEF1Bβ 		eEF1βEEF1B2
EEF1B2P1, EEF1B2P2, EEF1B2P3		GEF for eEF1A
eEF1BγeEF1γEEF1GStructural component
eEF1Bδ eEF1δEEF1DGEF for eEF1A
eEF1εeEF1εEEF1E1aminoacyl-tRNA synthetase complex member
Val-RS Val-RSVARSValyl tRNA synthetase

The precise manner eEF1B subunit attaches onto eEF1A varies by organ and species. In rabbits, Val-RS also participates in the complex by binding to eEF1Bδ.
eEF1A also binds actin.

Other species

Various species of green algae, red algae, chromalveolates, and fungi lack the EF-1α gene but instead possess a related gene called EFL. Although its function has not been studied in depth, it appears to be similar to EF-1α.
, only two organisms are known to have both EF-1α and EFL: the fungus Basidiobolus and the diatom Thalassiosira. The evolutionary history of EFL is unclear. It may have arisen one or more times followed by loss of EFL or EF-1α. The presence in three diverse eukaryotic groups is supposed to be the result of two or more horizontal gene transfer events, according to a 2009 review. A 2013 report finds 11 more species with both genes, and provided an alternative hypothesis that an ancestor eukaryote may have both genes. In all known organisms where both genes are present, EF-1α tends to be transcriptionally repressed. If the hypothesis holds true, scientists would expect to find an organism that has a repressed EFL and a fully-functioning EF-1α.
A 2014 review of EF-1α/EFL possessing eukaryotes considers both explanations insufficient on their own to explain the complex distribution of these two proteins in Eukaryotes.
In eukaryotes, a related GTPase called eRF3 participates in translation termination. The archaeal EF-1α, on the other hand, performs all functions carried by these subfunctionalized variants.