Final answer:
The initiation of protein synthesis in both prokaryotic and eukaryotic cells starts with the AUG start codon forming an initiation complex including mRNA, the small ribosomal subunit, initiation factors, and initiator tRNA.
Step-by-step explanation:
Initiation of protein synthesis begins with an mRNA binding to a ribosome such that the codon AUG is showing in the initiation complex. This marks the start of the translation process, where a transitional complex forms, and tRNA brings the first amino acid, methionine, to bind to the start codon on mRNA.
In both prokaryotic and eukaryotic systems, the initiation complex is formed differently, but the essentials are the same. Prokaryotes utilize a special form of methionine called N-formyl-methionine, while eurkaryotes use regular methionine. For ribosomal binding, prokaryotes rely on a Shine-Dalgarno sequence, whereas eukaryotic ribosomes attach to the 5' cap of the mRNA. Regardless, the initiation complex consists of the small ribosomal subunit, mRNA, initiation factors, and the initiator tRNA that recognizes the AUG codon.