The largest of the mammalian translation initiation factors, eIF3, consists of at least eight subunits ranging in mass from 35 to 170kDa. eIF3 binds to the 40 S ribosome in an early step of translation initiation and promotes the binding of methionyl-tRNAi and mRNA []. The N-terminal domain of eukaryotic translation initiation factor 3 subunit C mediates eIF3 binding to eIF1 and eIF5 [].
Eukaryotic translation initiation factor 3 subunit C (EIF3C) is a component of the eukaryotic translation initiation factor 3 (eIF-3) complex, which is required for several steps in the initiation of protein synthesis. EIF3C appears to be important for eIF3 activity []. Its N-terminal domain mediates eIF3 binding to eIF1 and eIF5 [], and its C-terminal PCI domain forms an important intermolecular bridge between eIF3 and the 40S ribosome [].
The eIF5-mimic protein 1/2 (also known as basic leucine zipper and W2 domain-containing proteins 2 and 1 (BZW2 and BZW1), respectively), are paralogous human proteins containing C-terminal HEAT domains that resemble the HEAT domain of eIF5 []. BZW1 plays an important role in the cell cycle and transcriptionally control the histone H4 gene during G1/S phase []. The Drosophila ortholog, kra (krasavietz) or exba (extra bases), may be involved in translational inhibition in neural development. The structure of this C-terminal W2 domain resembles that of a set of concatenated HEAT repeats [, , ].The W2 domain has a globular fold and is exclusively composed out of α-helices [, , ]. The structure can be divided into a structural C-terminalcore onto which the two N-terminal helices are attached. The core contains two aromatic/acidic residue-rich regions (AA boxes), which are important for mediating protein-protein interactions.
