eIF1A

Eukaryotic initiation factor 1A (eIF1A) is a small, highly conserved protein that participates in the initiation of translation in eukaryotes. It is a component of the 43S pre-initiation complex on the 40S ribosomal subunit and is essential for cap-dependent translation initiation in most organisms. eIF1A is widely conserved and has homologs in archaea and bacteria, reflecting its fundamental role in translation initiation.

Functionally, eIF1A operates during the scanning process that locates the start codon. It works together with other initiation factors, notably eIF1 and eIF3, to maintain the 40S subunit in a state that favors proper start codon recognition. eIF1A helps to regulate the position of the initiator tRNA and interacts with components near the ribosomal A-site and P-site, contributing to start codon fidelity. Once the AUG start codon is identified and the initiation complex commits to initiation, eIF2 delivers the initiator tRNA (Met-tRNAiMet), and 60S subunit joining proceeds; eIF1A is released as initiation progresses.

Structure and localization: eIF1A is a cytosolic protein that contains an N-terminal region (often flexible) and a conserved core domain, sometimes with an additional C-terminal tail that mediates interactions with ribosomal and initiation factors. The protein is present in most eukaryotes and is typically encoded by EIF1A; in some lineages related genes (e.g., EIF1AX) exist, reflecting gene family diversification.

Overall, eIF1A functions as a key regulator of start codon selection and ribosomal scanning, helping to ensure accurate translation initiation in eukaryotic cells.