Importance of Glu53 in the C-terminal region of brazzein, a sweet-tasting protein

• Published in: Journal of the science of food and agriculture Vol. 96; no. 9; pp. 3202 - 3206
• Main Authors: Lim, Jin-Kyung, Jang, Jin-Chul, Kong, Ji-Na, Kim, Myung-Chul, Kong, Kwang-Hoon
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.07.2016; John Wiley and Sons, Limited
• Subjects: Amino Acid Motifs; Amino Acid Substitution - genetics; Amino acids; Arginine - chemistry; brazzein; Construction; Escherichia coli - genetics; Food science; Foods; Gene Expression Regulation; Glu53; Glutamine - chemistry; Models, Molecular; mutagenesis; Mutagenesis, Site-Directed; mutants; Mutations; Plant Proteins - chemistry; Plant Proteins - genetics; Protein Conformation; protein sweeteners; Proteins; Receptors; Residues; Sensory perception; Sequence Analysis, Protein; site-directed mutagenesis; Structure-Activity Relationship; Sweetening Agents - chemistry; sweetness; sweetness determinant; Sweets; Taste; Glu53; mutagenesis; brazzein; sweetness determinant
• ISSN: 0022-5142; 1097-0010
• DOI: 10.1002/jsfa.7501

BACKGROUND The sweetness of brazzein, one of the known sweet proteins, is dependent on charges and/or structures of its specific amino acid side chains. As the residues in the C‐terminus of brazzein are known to play a critical role in sweetness, the currently unknown function of Glu53 requires further study. RESULTS To identify important residues responsible for the sweetness of the protein brazzein, four mutants of the Glu53 residue in the C‐terminal region of des‐pE1M‐brazzein, which lacks the N‐terminal pyroglutamate, were constructed using site‐directed mutagenesis. Mutations of Glu53 substitution to Ala or Asp significantly decreased the sweetness. On the other hand, a Lys mutation resulted in a molecule with sweetness similar to that of des‐pE1M‐brazzein. Mutation of Glu53 to Arg resulted in a molecule significantly sweeter than des‐pE1M‐brazzein, which agrees with previous findings showing that mutation with positively charged residues results in a sweeter protein. CONCLUSION Our results suggest that the residue at position 53 is crucial for the sweetness of brazzein, which may be interacting with the sweet‐taste receptor. © 2015 Society of Chemical Industry