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Tryptophan is the amino acid.
actin, myosin, troponin, tropomyosin are all contractile filaments which help in muscle action.
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A} TRYPTOPHAN..It's an Aromatic amino acid.
1 5 1
The other three are Muscle regulatory proteins.
TRYPTOPHAN is an acid
Actually , every amino acid has at least one amine and one ACID functional group as the name implies.