Protein Family Models

This family includes initiation factor 2B alpha, beta and delta subunits from eukaryotes, initiation factor 2B subunits 1 and 2 from archaebacteria and some proteins of unknown function from prokaryotes. Initiation factor 2 binds to Met-tRNA, GTP and the small ribosomal subunit. Members of this family have also been characterised as 5-methylthioribose- 1-phosphate isomerases, an enzyme of the methionine salvage pathway. The crystal structure of Ypr118w, a non-essential, low-copy number gene product from Saccharomyces cerevisiae, reveals a dimeric protein with two domains and a putative active site cleft [2]. [1]. 9520434. Archaeal translation initiation revisited: the initiation factor 2 and eukaryotic initiation factor 2B alpha-beta-delta subunit families. Kyrpides NC, Woese CR;. Proc Natl Acad Sci U S A 1998;95:3726-3730. [2]. 15215245. Crystal structure of yeast Ypr118w, a methylthioribose-1-phosphate isomerase related to regulatory eIF2B subunits. Bumann M, Djafarzadeh S, Oberholzer AE, Bigler P, Altmann M, Trachsel H, Baumann U;. J Biol Chem 2004; [Epub ahead of print] (from Pfam)

Date:

2024-12-02

Isomerizes methylthioribose-1-phosphate into methylthioribulose-1-phosphate; involved in methionine salvage pathway

Date:

2020-10-26

S-methyl-5-thioribose-1-phosphate isomerase catalyzes the interconversion of methylthioribose-1-phosphate (MTR-1-P) and methylthioribulose-1-phosphate (MTRu-1-P)

Date:

2017-07-10

This HMM, eIF-2B_rel, describes half of a superfamily, where the other half consists of eukaryotic translation initiation factor 2B (eIF-2B) subunits alpha, beta, and delta. It is unclear whether the eIF-2B_rel set is monophyletic, or whether they are all more closely related to each other than to any eIF-2B subunit because the eIF-2B clade is highly derived. Members of this branch of the family are all uncharacterized with respect to function and are found in the Archaea, Bacteria, and Eukarya, although a number are described as putative translation intiation factor components. Proteins found by eIF-2B_rel include at least three clades, including a set of uncharacterized eukaryotic proteins, a set found in some but not all Archaea, and a set universal so far among the Archaea and closely related to several uncharacterized bacterial proteins.

Date:

2024-12-02

The delineation of this family was based in part on a discussion and neighbor-joining phylogenetic study, by Kyrpides and Woese, of archaeal and other proteins homologous to the alpha, beta, and delta subunits of eukaryotic initiation factor 2B (eIF-2B), a five-subunit molecule that catalyzes GTP recycling for eIF-2. This clade is now recognized to include the methionine salvage pathway enzyme MtnA.

Gene:

mtnA

Date:

2021-04-27