Translation Initiation

Processed mRNAs, how does translation start, what does mRNA form

in the cytoplasm are ready for translation

Cap-binding proteins and poly-A binding proteins form a complex in the cytoplasm, facilitated by a translation initiation factor (eIF4G)

The resulting circularized mRNA is stable and able to be translated

Translation initiation complex, what binds first

forms and scans mRNA for a start codon

• The small subunit of the ribosome binds an initiator tRNA-Met (in the P-site) and other initiation factors

• This complex binds the mRNA near the 5’ end, and moves toward the 3’ end

• The complex will pause at an AUG, allowing the large subunit to bind

• The small subunit of the ribosome

binds an initiator tRNA-Met (in the P-site) and other initiation factors

• This complex binds the mRNA near the 5’ end, and moves toward the 3’ end

• The complex will pause at an AUG, allowing the large subunit to bind

Once the full ribosome is formed

on the start codon, translation elongation can proceed

• Another amino-acyl tRNA binds at the A site

• Peptide bond formation is catalyzed and Met is transferred to the A-site tRNA

• The initiator tRNA exits the ribosome, the ribosome moves toward the 3’ end, etc.

Once a ribosome moves away from the initiation site

another can bind and initiate