S1_IF2_alpha: The alpha subunit of translation Initiation Factor 2, S1-like RNA-binding domain. S1-like RNA-binding domains are found in a wide variety of RNA-associated proteins. Eukaryotic and archaeal Initiation Factor 2 (e- and aIF2, respectively) are heterotrimeric proteins with three subunits (alpha, beta, and gamma). IF2 plays a crucial role in the process of translation initiation. The IF2 gamma subunit contains a GTP-binding site. The IF2 beta and gamma subunits together are thought to be responsible for binding methionyl-initiator tRNA. The ternary complex consisting of IF2, GTP, and the methionyl-initiator tRNA binds to the small subunit of the ribosome, as part of a pre-initiation complex that scans the mRNA to find the AUG start codon. The IF2-bound GTP is hydrolyzed to GDP when the methionyl-initiator tRNA binds the AUG start codon, at which time the IF2 is released with its bound GDP. The large ribosomal subunit then joins with the small subunit to complete the initiation complex, which is competent to begin translation. The IF2a subunit is a major site of control of the translation initiation process, via phosphorylation of a specific serine residue. This alpha subunit is well conserved in eukaryotes and archaea but is not present in bacteria. IF2 is a cold-shock-inducible protein.
Jiyao W et al.(2023). "The conserved domain database in 2023.",