Initiation - ribosomal subunit in association with eIFs and...

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Initiation eIFs bind not only to the small ribosomal subunit (now of course the 40S ribosomal subunit), but some other eIFs bind to mRNA and another eIF binds to the initiator tRNA . The 5' cap of mRNA is important because the specific eIFs that bind to mRNA recognize and associate with the 5' cap [Also termed CAP binding proteins]. The single eIF that associates with the initiator tRNA carries a GTP (important later). The eIFs of mRNA and the initiator tRNA bring them to the 40S ribosomal subunit: the 40S subunit first associates with the very 5' end of mRNA. Then, the
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Unformatted text preview: ribosomal subunit , in association with eIFs and initiator tRNA, scans the mRNA until it reaches the AUG start codon. Scanning requires energy and is accompanied by ATP hydrolysis . It is not always the first AUG that is recognized as a start codon, sequences around first AUG might reduce efficiency of initiation so scanning continues to next AUG. • When AUG start codon reached, the GTP associated with the eIF of initiator tRNA is hydrolyzed . This causes all eIFs to be released from complex. Then the large ( 60S ) ribosomal subunit can bind....
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