3VHF: Plant Thaumatin I At Ph 8.0

Citation:
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 degrees 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 1.0A. Comparison to the crystal structure of thaumatin at pH 7.3 and 7.0 revealed the root-mean square deviation value of a Calpha 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 beta-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.
PDB ID: 3VHFDownload
MMDB ID: 99686
PDB Deposition Date: 2011/8/24
Updated in MMDB: 2012/05
Experimental Method:
x-ray diffraction
Resolution: 1.39  Å
Source Organism:
Similar Structures:
Biological Unit for 3VHF: monomeric; determined by author and by software (PISA)
Molecular Components in 3VHF
Label Count Molecule
Protein (1 molecule)
1
Thaumatin I
Molecule annotation
Chemicals (2 molecules)
1
2
* Click molecule labels to explore molecular sequence information.

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