Task: Class Definition Understanding (ontology: Sciences/Biology)

Which of the following definitions best describes 'N-terminal glycyl-L-lysyl-L-glutamate(1+) residue'?

A. A cationic dipeptide group obtained by protonation of the amino terminus of L-methionyl-L-tryptophyl residue; major species at pH 7.3.
B. A cationic dipeptide group obtained by protonation of both amino groups of L-leucyl-L-lysyl group; major species at pH 7.3.
C. A cationic dipeptide group obtained by protonation of the amino terminus of L-methionyl-L-glutaminyl residue; major species at pH 7.3.
D. A cationic peptidyl group obtained by protonation of the two amino groups of an glycyl-L-lysyl-L-glutamate residue.

Answer: A cationic peptidyl group obtained by protonation of the two amino groups of an glycyl-L-lysyl-L-glutamate residue.