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Eukaryotic initiation factors (eIFs) are proteins involved in the initiation phase of eukaryotic translation. These proteins help stabilize the formation of the functional ribosome around the start codon and also provide regulatory mechanisms in translation initiation. They form a complex with the small 40S ribosomal subunit and Met-tRNAMeti called the 43S preinitation complex (PIC). The 43S PIC recognizes and binds the five-prime cap structure of messenger RNA and promotes ribosomal scanning of mRNA to the AUG start codon. Recognition of the start codon by the Met-tRNA promotes GTP hydrolysis of specific initiation factors, resulting in the 60S ribosomal subunit binding to create the 80S ribosome. There exist many more eukaryotic initiation factors than prokaryotic initiation factors due to the greater biological complexity of eukaryotic cells. Eukaryotic translation requires at least nine eukaryotic initiation factors, described below. The protein RLI is known to have an essential, probably catalytic role in the formation of initiation complexes as well. == eIF4 (eIF4F) == (詳細はeIF4A, eIF4B, eIF4E, and eIF4G. eIF4F is often used to refer to the complex of eIF4A, eIF4E, and eIF4G. eIF4G is a 175.5-kDa scaffolding protein that interacts with eIF3 (see below), as well as the other members of the eIF4F complex. eIF4E recognizes and binds to the 5' cap structure of mRNA, while eIF4G binds to Poly(A)-binding protein, which binds the poly(A) tail, circularizing and activating the bound mRNA. eIF4Aa DEAD box RNA helicaseis important for resolving mRNA secondary structures. eIF4B contains two RNA-binding domainsone non-specifically interacts with mRNA, whereas the second specifically binds the 18S portion of the small ribosomal subunit. It acts as an anchor, as well as a critical co-factor for eIF4A. It is a substrate of S6K, and, when phosphorylated, it promotes the formation of the pre-initiation complex. In vertebrates, eIF4H is an additional initiation factor with similar function to eIF4B. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「eukaryotic initiation factor」の詳細全文を読む スポンサード リンク
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