Translation starts at the three-base codon for the amino acid methionine in almost every known instance. The sequence of this codon is AUG. Both protein and RNA components can be found in the two subunits that make up proteins. The smaller ribosomal subunit's responsibility is to identify the AUG codon, which will serve as the beginning of translation (called the initiation codon). Finding the proper AUG is not an easy task, even though always starting at AUG helps alleviate the reading frame problem. When there are many AUG codons in an mRNA, the small ribosomal subunit must identify the proper one in order to produce the desired protein.