岩豆凝集素分子中色氨酸残基的化学修饰及其荧光光谱研究

从岩豆（Ｍｉｌｌｅｔｔｉａ ｄｉｅｌｓｉａｎａ Ｈａｒｍｓ ｅｘ Ｄｉｅｌｓ）种妇中分离纯化得到的岩豆凝集素（简称ＭＤＬ）经链霉蛋白酶水解,测得其分子中含有４个色氨酸（Ｔｒｐ）残基。用Ｎ－溴代丁二酰亚胺（ＮＢＳ）对ＭＤＬ分子中的色氨酸残基进行化学修饰,在无变性剂存在下有３．６个Ｔｒｐ残基被修饰,在变性条件下可修饰３．８个Ｔｒｐ残基。修饰后ＭＤＬ活性均丧失,且甘露糖对ＭＤＬ活性雎有保护作用。表明Ｔｒ

CHEMICAL MODIFICATION OF TRYPTOPHAN RESIDUES AND STUDIES ON LECTIN FROM MILLETTIA DIELSIANA HARMS EX DIELS

The purified Millettia dielsiana Harms ex Diels Lectin(MDL) was studied by chemical modification of typtophan residues and fluorescence spectroscopy. Result from pronase hydrolysis assay showed that there were four tryptophan(Trp) residues in MDL molecule. Modification of Trp residues with N-Bromosuccinimide(NBS) induced obvious changes in the fluorescence emission spectra of MDL and resulted in a complete loss of hemagglutinating activity. There were 3.6 Trp residues modified as demonstrated by modification with NBS in native state and 3.8 Trp residues modified in denaturing condition ［c(urea)=8 mol/L］. The research also found that mannose could prevent MDL from losing its activity after being modified by NBS. It indicated that Trp residues were essential for the activity of MDL and involved at carbohydrate-binding site. Results from fluorescence spectra also implied that Trp residues were located in the hydrophobic pocket of the surface of MDL.Fig 3, Ref 8