Structural highlights
Publication Abstract from PubMedOne of the sweetest proteins found in tropical fruits (with a threshold of 50nM), thaumatin, is also used commercially as a sweetener. Our previous study successfully produced the sweetest thaumatin mutant (D21N), designated hyper-sweet thaumatin, which decreases the sweetness threshold to 31nM. To investigate why the D21N mutant is sweeter than wild-type thaumatin, we compared the structure of the D21N mutant solved at a subatomic resolution of 0.93A with that of wild-type thaumatin determined at 0.90A. Although the overall structure of the D21N mutant resembles that of wild-type thaumatin, our subatomic resolution analysis successfully assigned and discriminated the detailed atomic positions of side-chains at position 21. The relative B-factor value of the side-chain at position 21 in the D21N mutant was higher than that of wild-type thaumatin, hinting at a greater flexibility of side-chain at 21 in the hyper-sweet D21N mutant. Furthermore, alternative conformations of Lys19, which is hydrogen-bonded to Asp21 in wild-type, were found only in the D21N mutant. Subatomic resolution analysis revealed that flexible conformations at the sites adjacent to positions 19 and 21 play a crucial role in enhancing sweet potency and may serve to enhance the complementarity of electrostatic potentials for interaction with the sweet taste receptor. Subatomic structure of hyper-sweet thaumatin D21N mutant reveals the importance of flexible conformations for enhanced sweetness.,Masuda T, Okubo K, Murata K, Mikami B, Sugahara M, Suzuki M, Temussi PA, Tani F Biochimie. 2019 Feb;157:57-63. doi: 10.1016/j.biochi.2018.10.020. Epub 2018 Oct, 31. PMID:30389513[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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