Multiple Choice
Which level of protein structure is defined by the actual sequence of amino acids present in the polypeptide chain?
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4. Protein Structure
Primary Structure of Protein
Multiple Choice
In most newly synthesized proteins, which amino acid is incorporated first at the N-terminus during translation initiation?
A
Proline (Pro)
B
Methionine (Met)
C
Glycine (Gly)
D
Tryptophan (Trp)
Verified step by step guidance1
Understand that during translation initiation in eukaryotes, the first amino acid incorporated at the N-terminus of a newly synthesized protein is determined by the start codon on the mRNA, which is typically AUG.
Recall that the AUG codon codes for the amino acid methionine (Met), which is universally the first amino acid incorporated during protein synthesis in both prokaryotes and eukaryotes.
Recognize that although methionine is the first amino acid incorporated, it may be removed later during post-translational modifications, but it is always the initial amino acid during translation initiation.
Note that other amino acids like proline, glycine, or tryptophan are incorporated later in the protein sequence according to their respective codons, but they are not the initiating amino acid.
Therefore, the correct answer is methionine (Met) because it corresponds to the start codon AUG, which signals the beginning of translation and the first amino acid incorporated.
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