A significant difference between prokaryotes and eukaryotes in initiation of translation is that in prokaryotes, the large subunit of the ribosome binds after the mRNA; in eukaryotes, the large subunit binds before the mRNA. many more initiation factors are required for prokaryotes than for eukaryotes. in prokaryotes, base-pairing between the mRNA and an rRNA determines which start codon to use; in eukaryotes, the small subunit begins scanning the mRNA at the 5' cap until it reaches the first start codon. GTP hydrolysis is required for prokaryotic initiation, but not eukaryotic initiation.