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The Flexible Loop is a New Sweetness Determinant Site of the Sweet-Tasting Protein: Characterization of Novel Sweeter Mutants of the Single-Chain Monellin (MNEI). | LitMetric

AI Article Synopsis

  • The single-chain monellin (MNEI) has the same level of sweetness as natural monellin, and specific mutations in its loop regions were studied to determine their impact on sweetness.
  • Mutations affecting positive-charge residues consistently reduced sweetness, while changes in negative-charge residues produced mixed results; notably, the E50N mutation significantly increased sweetness.
  • Using techniques like homology modeling and molecular dynamics simulations, researchers identified the flexible loop L23 as a key region that influences sweetness in the protein, leading to the development of sweeter mutant variants for potential use in designing sweet-tasting proteins.

Article Abstract

The single-chain monellin (MNEI) displays same sweet potency as the natural monellin protein. To identify critical residues determining its sweetness, residues located at the loops region were selected for mutagenesis analysis. Mutations of positive-charge residues R31, R53, and R82 consistently led to obvious decrease of sweetness, whereas mutations of negative-charge residues resulted in variable sweet potency. Of note, the E50N mutant in the loop region linking the 2 natural chains showed significantly increased sweetness. Mutations of this residue to M or K led to similar effects, in accordance with the so-called wedge model for explanation of the sweet protein-receptor interaction. Homology modeling was carried out with the firstly reported crystal structure of sweet taste receptor (from medaka fish) as the template, and molecular docking and dynamics simulations suggested that flexible conformations of specific residues located in the loops region play essential roles for the interaction with the receptor and the sweetness of the protein. Moreover, obvious additive effects were found for the sweetness as 2 double-site mutants (E50N/Y65R and E2N/E50N) displayed increased sweetness than their single-site mutants. Our results revealed the flexible loop L23 linking the 2 natural chains as a novel sweetness determinant site of the sweet protein monellin and raised a series of new sweeter mutants, which could provide helpful guidance for molecular designing the sweet-tasting proteins.

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Source
http://dx.doi.org/10.1093/chemse/bjz057DOI Listing

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