THE TASTE-ACTIVE REGIONS OF MONELLIN, A POTENTLY SWEET PROTEIN

Monellin, a protein found in the berries of the West African plant Dio scoreophyllum cumminsii, is one of the most potently sweet compounds k nown. The native three-dimensional structure of monellin is required f or sweetness, and this protein has been the subject of intense researc h in an attempt at understanding the structural basis for its taste ac tivity. We have used structure-based site-directed mutagenesis to deli neate the taste-active site(s) of monellin, and we present these resul ts, along with similar work from M. Kohmura, Y. Ariyoshi and coworkers , in the light of the three-dimensional structure of this protein. The mutagenesis work suggests that at least four residues, located N-term inal to the alpha-helix, form part of a taste-active region of monelli n. In addition, there is evidence that a second region, formed by,resi dues in the fourth and fifth beta-strands, may also be contributing to monellin's activity.