While these general concepts are widely conserved, some of the finer details in this sort of regulation have been proven to differ between prokaryotic and eukaryotic organisms.
This stretch of four to nine purine residues are located upstream the initiation codon and hybridize to a pyrimidine-rich sequence near the 3' end of the 16S RNA within the 30S bacterial ribosomal subunit.
[5] Generally, these initiation factors are expressed in equal proportion to ribosomes, however experiments using cold-shock conditions have shown to create stoichiometric imbalances between these translational machinery.
In this case, two to three fold changes in expression of initiation factors coincide with increased favorability towards translation of specific cold-shock mRNAs.
In fact, some bases proximal to the stop codon suppress the efficiency of translation termination by reducing the enzymatic activity of the release factors.
This base pairing comes about by the scanning mechanism that ensues once the small 40S ribosomal subunit binds the 5' untranslated region (UTR) of mRNA.
The usage of this scanning mechanism, in opposition to the Shine-Dalgarno sequence that was referenced in prokaryotes, is the ability to regulate translation through upstream RNA secondary structures.
[10] Serine kinases, GCN2, PERK, PKR, and HRI are examples of detection mechanisms for differing cellular stresses that respond by slowing translation through eIF2 phosphorylation.
While prokaryotes are able to undergo both cellular processes simultaneously, the spatial separation that is provided by the nuclear membrane prevents this coupling in eukaryotes.