Initiation of translation

Definition

Initiation of translation is the first phase of protein synthesis where the ribosome assembles around the target mRNA. This process requires initiation factors and a specific sequence on the mRNA called the start codon.

5 Must Know Facts For Your Next Test

1. The start codon for initiation in most organisms is AUG, which codes for methionine.
2. Initiation factors (IFs in prokaryotes and eIFs in eukaryotes) are essential for the proper assembly of the ribosome on the mRNA.
3. In bacteria, the Shine-Dalgarno sequence aligns the mRNA on the ribosome, while in eukaryotes, this role is played by the Kozak sequence.
4. The small ribosomal subunit binds to mRNA first, followed by the large subunit after placement of initiator tRNA at the P site.
5. GTP hydrolysis provides energy for several steps during initiation, including binding of initiation factors and assembly of ribosomal subunits.

Review Questions

Related terms

Ribosome:

A molecular complex made up of rRNA and proteins that synthesizes proteins based on mRNA sequences.

Start Codon:

A specific nucleotide triplet (usually AUG) in mRNA that signals where translation begins.

Shine-Dalgarno Sequence: A ribosomal binding site in bacterial and archaeal mRNA, generally located upstream of the start codon.