Atomic structure of the sweet-tasting protein thaumatin I at pH 8.0 reveals the large disulfide-rich region in domain II to be sensitive to a pH change

Abstract

Thaumatin, an intensely sweet-tasting plant protein, elicits a sweet taste at 50 nM. Although the sweetness remains when thaumatin is heated at 80 °C for 4h under acid conditions, it rapidly declines when heating at a pH above 6.5. To clarify the structural difference at high pH, the atomic structure of a recombinant thaumatin I at pH 8.0 was determined at a resolution of 1.0Å. Comparison to the crystal structure of thaumatin at pH 7.3 and 7.0 revealed the root-mean square deviation value of a Cα atom to be substantially greater in the large disulfide-rich region of domain II, especially residues 154-164, suggesting that a loop region in domain II to be affected by solvent conditions. Furthermore, B-factors of Lys137, Lys163, and Lys187 were significantly affected by pH change, suggesting that a striking increase in the mobility of these lysine residues, which could facilitate a reaction with a free sulfhydryl residue produced via the β-elimination of disulfide bonds by heating at a pH above 7.0. The increase in mobility of lysine residues as well as a loop region in domain II might play an important role in the heat-induced aggregation of thaumatin above pH 7.0.

A Hypersweet Protein: Removal of The Specific Negative Charge at Asp21 Enhances Thaumatin Sweetness

“…In reality the alternation of basic, acidic and neutral residues in an entangled patchwork is ultimately responsible of the extremely high affinity of sweet proteins to the sweet receptor. During the past few years we have explored the structure-activity relationship of thaumatin in great depth 5 6 7 26 27 28 29 30 . We capitalized on such knowledge to choose the right acidic residues to mutate.…”

Análisis De Las Fuerzas Del Mercado Dendroenergético en La Vereda Cajete Del Municipio De Popayán

“…Es una proteína de elevado poder edulcorante, presente en el fruto de la planta Thaumatococcus danielli Benth, que tiene una alta solubilidad en agua, y se caracteriza por ser altamente estable a pH ácido, así como también al calor [35]. Existen por lo menos 5 formas de esta proteína en la planta, con dos componentes principales (taumatina I y II) y tres componentes minoritarios (taumatina a, b y c) [36]. Todas cuentan con la aprobación en su uso y consumo por la Unión Europea (aditivo E 957), y por su bajo aporte calórico, se convierte en una propuesta médica para confrontar estilos de vida relacionados con problemas frecuentes en la salud, tales como la hipertensión, hiperlipidemia, diabetes y obesidad [37].…”

“…La taumatina cuenta con un dulzor relativo equivalente a 200.000-300.000 (valor expresado en relación a la sacarosa con un dulzor relativo de 100) [36]. De igual manera, se clasifica a la taumatina como un edulcorante natural, intenso y con una contribución energética despreciable; se cataloga este edulcorante con un valor de potencia de 2500 veces respecto a la sacarosa [40].…”

Towards a high-throughput system for high-pressure cooling of cryoprotectant-free biological crystals

“…9(a). It is also worth mentioning that pressure affects the regions near Lys67, Lys137 and Lys163, which are key residues playing an important role in the sweetness and/or the solubility of thaumatin, the conformational mobility of which is highly sensitive to the solvent conditions (Masuda et al, 2012).…”