The Complete Amino‐Acid Sequence of the Sweet Protein Thaumatin I

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Abstract
The primary structure of the sweet‐tasting protein thaumatin has been elucidated. The protein consists of a single polypeptide chain of 207 residues. The sequence of the N‐terminal part of the chain was determined by sequenator analysis. As the protein contains only one methionine residue, it was possible to deduce the N‐terminal sequence of the C‐terminal cyanogen bromide fragment by automatic sequencing of the cyanogens‐bromide‐cleaved, succinylated protein. To arrive at the sequence of the whole protein tryptic and Staphylococcus protease peptides, together with chymotryptic peptides and a 2‐(2‐nitrophenylsulfenyl)‐3‐methyl‐3′‐bromoindolenine (BNPS‐skatole) fragment were also sequenced.Comparing the amino acid sequence of thaumatin with that of the other sweet‐tasting protein, monellin, we have located five sets of identical tripeptides. Since immunological cross‐reactivity of thaumatin antibodies with monellin has recently been described, one or more of these tripeptides might be part of a common antibody recombination site and possibly be involved in the interaction with the sweet‐taste receptor.