The initiator AUG in prokaryotes codes for the amino acid Methionine. In the context of protein synthesis, AUG serves as the start codon, signaling the beginning of translation.
When the ribosome assembles on the mRNA strand, it looks for this specific AUG sequence to start synthesizing the protein. In prokaryotes, the ribosome binds to the Shine-Dalgarno sequence located upstream of the AUG codon, ensuring proper positioning for translation initiation. As a result, the first tRNA molecule carrying Methionine recognizes this AUG codon, bringing the first amino acid into the growing polypeptide chain.
It’s also important to note that in eukaryotes, the first amino acid may also be Methionine, but there are differences in the context of how translation is initiated. In both cases, however, the role of AUG as the start codon remains a fundamental aspect of the genetic code.