Cysteine, tryptophan, and methionine are not common amino acids: together, they constitute approximately 5 percent of the amino acids in a typical protein. Four amino acids—leucine, serine, lysine, and glutamic acid—are the most abundant amino acids, constituting 32 percent of all the residues in a typical protein.
#Unit 1. Molecules and their Interaction Relevant to Biology#Amino Acids#Part B Pointers
