Ribosome Initiation is the first step in the translation of mRNA to a protein. It requires initiation factors IF1, IF2 and IF3 as well as GTP for energy and an initiator tRNA known as fMet-tRNAfMet. Initiation in prokaryotes occurs as follows:
- IF1 and IF3 bind to the free 30S subunit of the 70S ribosome.
- A GTP/IF2 complex then binds to the 30S subunit.
- The 30S subunit then binds to the 16S complementary region of the mRNA strand.
- A charged initiator tRNA can now bind which causes the release of IF3.
- The 50S subunit binds forming the ribosome, displacing IF1 and IF 2 and hydrolysing GTP to GDP. This step is the energy consuming step.