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

► Structure of a recombinant thaumatin at pH 8.0 determined at a resolution of 1.0 Å. ► Substantial fluctuations of a loop in domain II was found in the structure at pH 8.0. ► B-factors for Lys137, Lys163, and Lys187 were significantly affected by pH change. ► An increase in mobility might play an important role in the heat-induced aggregation.