Biochemistry 3381A Chapter Notes - Chapter 30.6: Start Codon, Reticulocyte, Eef2
9 Oct 2017
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Stage 1: formation of 43s preinitiation and eif4f complexes. Initiation factors eif1, eif1a, eif3, eif5 bind to 40s ribosomal subunit: met-trnai. Stage 2: binding of mrna cap structure: usually binding of 43s complex requires recognition of mrna methyl-g-cap by eif4f, due to presence of internal 40s binding site, upstream of initiation codon. In some cases, initiation can occur independently of the cap structure: eif(cid:886)f binds (cid:887)" cap of mrna through contact between eif(cid:886)e and cap structure, eif4g interacts with polya binding protein, circularizing the mrna. Stage 3: scanning by 43s ribosomal complex of the 40s subunit in search of aug. Stage 4: unwinding of secondary structure: eif4g is the bridge between eif4e, polya tail, and 40s subunit. Interactions between (cid:887)" terminal methyl-gtp cap and (cid:885)" polya tail initiation (cid:887)"-(cid:885)" scanning: (cid:886)(cid:885)s unable to scan through secondary structure in the (cid:887)" utr, eif4a, other helicases/accessory proteins unwind the secondary structures in mrna in an. Atp-dependent manner: eif4b and eif4h enhance eif4a.
