eIF2B is a protein found in eukaryotes. It is the guanine nucleotide exchange factor for the eukaryotic initiation factor 2 and therefore converts the inactive eIF2-GDP to the active eIF2-GTP. This activation is hindered by phosphorylation of the alpha subunit of eIF2, which leads to a stable eIF2α-P-GDP-eIF2B complex and therefore inhibits translation initiation. [1]
Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific three-dimensional structure that determines its activity.
Eukaryotes are organisms whose cells have a nucleus enclosed within membranes, unlike prokaryotes, which have no membrane-bound organelles. Eukaryotes belong to the domain Eukaryota or Eukarya. Their name comes from the Greek εὖ and κάρυον. Eukaryotic cells also contain other membrane-bound organelles such as mitochondria and the Golgi apparatus, and in addition, some cells of plants and algae contain chloroplasts. Unlike unicellular archaea and bacteria, eukaryotes may also be multicellular and include organisms consisting of many cell types forming different kinds of tissue. Animals and plants are the most familiar eukaryotes.
Guanine nucleotide exchange factors (GEFs) are proteins or protein domains that activate monomeric GTPases by stimulating the release of guanosine diphosphate (GDP) to allow binding of guanosine triphosphate (GTP). A variety of unrelated structural domains have been shown to exhibit guanine nucleotide exchange activity. Some GEFs can activate multiple GTPases while others are specific to a single GTPase.
Human genes which encode eIF-2B proteins include:
- EIF2B1 – alpha subunit (26kDa)
- EIF2B2 – beta subunit (39kDa)
- EIF2B3 – gamma subunit (58kDa)
- EIF2B4 – delta subunit (67kDa)
- EIF2B5 – epsilon subunit (82kDa)
Translation initiation factor eIF-2B subunit alpha is a protein that in humans is encoded by the EIF2B1 gene.
Translation initiation factor eIF-2B subunit beta is a protein that in humans is encoded by the EIF2B2 gene.
Translation initiation factor eIF-2B subunit gamma is a protein that in humans is encoded by the EIF2B3 gene.
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- ↑ "eIF2B, a mediator of general and gene-specific translational control". Biochem Soc Trans. 33 (Pt 6): 1487–92. Dec 2005. doi:10.1042/BST20051487. PMID 16246152.
