Department of Food Science and Nutrition, Nara Women's University, Nara 630-8506, Japan.
FEBS Lett. 2013 Jun 19;587(12):1767-72. doi: 10.1016/j.febslet.2013.04.026. Epub 2013 May 7.
Miraculin, a glycoprotein that modifies sour tastes into sweet ones, belongs to the Kunitz-type soybean trypsin inhibitor (STI) family. To clarify the functional relation of miraculin with Kunitz-type STIs, we investigated its subcellular localization and trypsin inhibitory activity. In transgenic Arabidopsis thaliana, miraculin, fused to yellow fluorescent protein, localized to and outside the plasma membrane depending on the putative secretion signal peptide. When transgenic seedlings were cultured in liquid medium, miraculin was present in the supernatant only after cellulase treatment. No trypsin inhibitory activity was detected in native or recombinant miraculin. In conclusion, miraculin is secreted outside the plasma membrane through the function of a signal peptide, conserved in Kunitz-type STIs, whereas its trypsin inhibitory activity may be lost during its evolution.
神秘果素是一种糖蛋白，可将酸味转变为甜味，属于 Kunitz 型大豆胰蛋白酶抑制剂 (STI) 家族。为了阐明神秘果素与 Kunitz 型 STI 的功能关系，我们研究了它的亚细胞定位和胰蛋白酶抑制活性。在转基因拟南芥中，与黄色荧光蛋白融合的神秘果素定位于质膜内外，这取决于假定的分泌信号肽。当转基因幼苗在液体培养基中培养时，只有在用纤维素酶处理后，神秘果素才会出现在上清液中。天然或重组神秘果素均未检测到胰蛋白酶抑制活性。总之，神秘果素通过 Kunitz 型 STI 中保守的信号肽的功能分泌到质膜外，而其胰蛋白酶抑制活性可能在其进化过程中丢失。
