FAMILY OF LOW-CALORIC SWEETENERS--3-D STRUCTURES

THE THAUMATINS ARE A FAMILY OF NATURALLY OCCURRING PLANT-DERIVED PROTEINS WITH A SWEET TASTE MANY THOUSANDFOLD MORE INTENSE THAN SUGAR. THESE PROTEINS ARE GENERALLY REGARDED AS SAFE, ARE APPROVED FOR USE AS FOOD ADDITIVES IN NUMEROUS COUNTRIES, DO NOT PROMOTE WEIGHT GAIN, AND HAVE NOTBEEN IMPLICATED IN THE FORMATION OF DENTAL CARIES. XOMA CORPORATION HAS PURIFIED THE TWO MAJOR SPECIES OF PLANT THAUMATIN. DIFFRACTION-GRADE CRYSTALS HAVE BEEN GROWNFOR BOTH PROTEINS, AND REFLECTION DATA ARE BEING COLLECTED. SEVERAL HEAVY ATOM DERIVATIVES HAVE ALREADY BEEN GENERATED. IN ADDITION TO THE NATIVE THAUMATINS THAT WILL FORM THE BASIS FOR CRYSTALLOGRAPHIC ANALYSES, A LIBRARY OF THAUMATIN VARIANTS HAS BEEN PRODUCED BY USING ALTERED SYNTHETIC GENES EXPRESSED VIA A YEAST SECRETION SYSTEM. EACH OF THESE HAS BEEN PURIFIED AND CATEGORIZED AS TO STABILITY AND TASTE CHARACTER. DURING THE INITIAL PHASE OF THIS SUDY, THE STRUCTURE OF THE TWO MAJOR PLANT PROTEINS WILL BE DETERMINED. LATER STUDIES WILL COMPARE THESE TO THE THREE-DIMENSIONAL STRUCTURE OF THAUMATIN DERIVATIVES HAVING ALTERED TASTE PROPERTIES. THE DATE WILL BE USED TO MAP THE THAUMATIN DOMAINS THAT AFFECT TASTE AND THE QUALITY OF SWEETNESS PERCEPTION. BASED ON THESE STRUCTURAL ANALYSES, ATTEMPTS WILL BE MADE TO IDENTIFY OR FURTHER DESIGN SAFE, LOW-CALORIE, NONCARIOGENIC SWEETENERS WITH SPECIFIC TASTE AND STABILITY CHARACTERISTICS.