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

Authors


  • Dedicated to Prof. Dr E. Havinga, professor of Organic Chemistry at the State University of Leiden, on the occasion of his seventieth birthday.

  • Note. Peptides: T, tryptic; C, chymotryptic; SP, Staphylococcus protease; CB cyanogen bromide fragment; BNPS, BNPS-skatole fragment.

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.

Abbreviations
Dansyl

5-dimethylaminonaphthalene-1-sulfonyl

BNPS-skatole

2-(2-nitrophenylsulfenyl)-3-methyl-3′-bromoindolenine

Pth

phenylthiohydantoin

quadrol

N,N,N′,N′-tetrakis-(2-hydroxypropyl)-ethylene diamine

Enzymes
 

Trypsin (EC 3.4.21.4)

 

α-chymotrypsin (EC 3.4.21.1)

 

Staphylococcus aureus protease V 8 (EC 3.4.12.–)

Ancillary