initiation of protein synthesis in prokaryotes

Formation of the 70S initiation complex

Schematic of the initiation of protein synthesis in prokaryotes

1.  Binding of IF1 & IF3 to an empty 70S ribosome dissociates it into 50S and 30S subunits.

2.   a.  5' region of mRNA binds to 16S rRNA of free 30S ribsomal subunit, IF3 is released.

b.  Initiator fMet-tRNA^fMet carried by IF2-GTP binds to P site of 30S ribsomal subunit.

3.  Free 50S ribosomal subunit binds, IF1 & IF2-GDP + P_i  are released.

Certain details of the process remain uncertain.  For example, the exact order of binding of IF1, IF2, IF3, tRNA, and mRNA is unclear.  The above is one model.

Next:  Initiation of translation in eukaryotes

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