Atomic structure of recombinant thaumatin II reveals flexible conformations in two residues critical for sweetness and three consecutive glycine residues

Abstract

Thaumatin, an intensely sweet-tasting protein used as a sweetener, elicits a sweet taste at 50 nM. Although two major variants designated thaumatin I and thaumatin II exist in plants, there have been few dedicated thaumatin II structural studies and, to date, data beyond atomic resolution had not been obtained. To identify the detailed structural properties explaining why thaumatin elicits a sweet taste, the structure of recombinant thaumatin II was determined at the resolution of 0.99 Å. Atomic resolution structural analysis with riding hydrogen atoms illustrated the differences in the direction of the side-chains more precisely and the electron density maps of the C-terminal regions were markedly improved. Though it had been suggested that the three consecutive glycine residues (G142-G143-G144) have highly flexible conformations, G143, the central glycine residue was successfully modelled in two conformations for the first time. Furthermore, the side chain r.m.s.d. values for two residues (R67 and R82) critical for sweetness exhibited substantially higher values, suggesting that these residues are highly disordered. These results demonstrated that the flexible conformations in two critical residues favoring their interaction with sweet taste receptors are prominent features of the intensely sweet taste of thaumatin.

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.…”

Bioproduction of the Recombinant Sweet Protein Thaumatin: Current State of the Art and Perspectives

“…Two key amino acid residues (R82 and K67) were identified that played a key role in binding to the taste receptors. A further study on the intensely sweet taste of thaumatin II was made by Masuda et al (2014). Masuda et al (2010) used an expression vector that contained three copies of the thaumatin I gene to drive up the yield to 100 mg/L.…”

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

“…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].…”