Ozaki M, Amakawa T, Ozaki K, Tokunaga F
Department of Biology, Faculty of Science, Osaka University, Japan.
J Gen Physiol. 1993 Aug;102(2):201-16. doi: 10.1085/jgp.102.2.201.
Flies have taste cells specifically sensitive to sweetness. It has been suggested that the cells possess two types of receptor sites covering the receptive field of sweetness. By affinity electrophoresis with the site-specific inhibitory polysaccharides, two types of sugar-binding protein were isolated from the labellar extract of the blowfly. These proteins showed consistent sugar-binding specificities and affinities with the two types of receptor sites for sweetness, respectively. The dissociation constant of the protein-sugar complex varies 100-400 mM and the molecular weight of one type of the protein is 27,000, while that of the other is 31,000 or 32,000. Both proteins were water insoluble and were also detected in the isolated chemosensilla. Thus they are probably located on the taste receptor membrane, and the proteins are likely to act as the taste receptor molecules for sweetness in the fly.
苍蝇具有对甜味特别敏感的味觉细胞。有人提出，这些细胞拥有两种覆盖甜味感受野的受体位点。通过使用位点特异性抑制多糖的亲和电泳，从绿头苍蝇的唇叶提取物中分离出了两种糖结合蛋白。这些蛋白质分别与两种甜味受体位点表现出一致的糖结合特异性和亲和力。蛋白质 - 糖复合物的解离常数在100 - 400 mM之间变化，其中一种蛋白质的分子量为27,000，而另一种的分子量为31,000或32,000。这两种蛋白质都不溶于水，在分离出的化学感受器中也能检测到。因此，它们可能位于味觉受体膜上，并且这些蛋白质可能充当苍蝇甜味的味觉受体分子。
