MIF4G

MIF4G is a protein domain name used to describe the middle region of the eukaryotic initiation factor 4G (eIF4G) family and other proteins that carry this domain. The acronym originates from “MIF4G,” standing for the middle portion of the initiation factor 4G. The term is applied to a conserved helical domain that serves as a scaffold for interactions involved in translation initiation.

In terms of structure and interactions, the MIF4G domain is typically part of larger multi-domain eIF4G proteins. It forms a solenoid-like surface that primarily binds the RNA helicase eIF4A, aiding in the recruitment and coordination of helicase activity during the scanning of 5' untranslated regions. This domain works in concert with other regions of eIF4G, including domains that bind the cap-binding protein eIF4E and, via separate motifs, the poly(A)-binding protein. The overall result is a platform that promotes cap-dependent translation initiation by helping to recruit and organize initiation factors at the 5' end of mRNA.

Occurrence and evolution: MIF4G is found in eukaryotic organisms and is a characteristic feature of eIF4G family members. Some organisms also harbor proteins with one or more additional MIF4G repeats, reflecting domain duplication events. The domain is not typically found in bacteria and is associated with eukaryotic mechanisms of translation initiation.

See also: eukaryotic initiation factor 4G (eIF4G), eIF4A, PABP.

Notes: The MIF4G domain is one component of the larger eIF4G architecture that serves to integrate cap recognition, helicase activity, and mRNA recruitment during the initiation of translation.