| Type: | Family | Name: | Initiation factor 2B-related |
| Description: | Initiation factor 2 binds to Met-tRNA, GTP and the small ribosomal subunit. The eukaryotic translation initiation factor EIF-2B is a complex made up of five different subunits, alpha, beta, gamma, delta and epsilon, and catalyses the exchange of EIF-2-bound GDP for GTP. This family includes initiation factor 2B alpha, beta and delta subunits from eukaryotes; related proteins from archaebacteria and IF-2 from prokaryotes and also contains a subfamily of proteins in eukaryotes, archaeae (e.g. Pyrococcus furiosus), or eubacteria such as Bacillus subtilisand Thermotoga maritima. Many of these proteins were initially annotated as putative translation initiation factors despite the fact that there is no evidence for the requirement of an IF2 recycling factor in prokaryotic translation initiation. Recently, one of these proteins from B. subtilis has been functionally characterised as a 5-methylthioribose-1-phosphate isomerase (MTNA) []. This enzyme participates in the methionine salvage pathway catalysing the isomerisation of 5-methylthioribose-1-phosphate to 5-methylthioribulose-1-phosphate []. The methionine salvage pathway leads to the synthesis of methionine from methylthioadenosine, the end product of the spermidine and spermine anabolism in many species. | Short Name: | IF-2B-related |
