| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2012: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2011: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2010: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
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| Research Abstract |
The crystal structure of a recombinant thaumatin I was determined to a resolution of 1.1 A (PDB:3AL7). The crystallographic structure of one of its variants, thaumatin II, was determined at a resolution of 1.27 A (PDB:3AOK). The results showed the critical positive charges are disordered and the flexibility and fluctuation of these side chains would be suitable for interaction with sweet receptors. The atomic structure of a recombinant thaumatin at pH 8.0 was determined at a resolution of 1.0 A (PDB:3VJQ). The results suggested a striking increase in the mobility of some 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. Various mutants of thaumatin were prepared and their sweetness were quantitatively evaluated by cell-based assays using HEK293 cells expressing human sweet receptors. Chimeric human- mouse sweet receptors were constructed and their responses to sweeteners were investigated. The results showed the cysteine-rich domain of human T1R3 is important for the response to thaumatin.
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