基于结构域活性分析的大肠杆菌T蛋白结构研究

DOMAIN ACTIVITY BASED PROTEIN STRUCTURE STUDY OF T-PROTEIN FROM Escherichia coli

大肠杆菌T蛋白含有三个结构域:分支酸变位酶、预苯酸脱氢酶和调节结构域。文章作者分段克隆了T蛋白的分支酸变位酶、预苯酸脱氢酶和调节结构域等片段,并对其进行了活性研究。研究发现,定位于N末端的分支酸变位酶结构域的比活性虽然不高,而稳定性较好;同时拥有调节结构域和预苯酸脱氢酶结构域的C末端片段,其预苯酸脱氢酶比活性的剩余百分率虽然高于分支酸变位酶结构域,但稳定性较差。作者进而表达了C末端切除38个氨基酸的T/1-336片段,发现预苯酸脱氢酶活性彻底丧失,而其分支酸变位酶和调节结构域的活性却基本保留。这说明T蛋白中分支酸变位酶结构域拥有一个相对独立、完整的结构,而预苯酸脱氢酶结构域和调节结构域交织共存,结构松散。

T-protein from Escherichia coli consists of three domains： chorismate mutase, prephenate dehydrogenase and a regulatory domain. In this study, the domain activity of several fragments from T-protein was evaluated. It was found that chorismate mutase domains＇ retained less activity, but was more stable, prephenate dehydrogenase domain retained more activity, but less stability. It lost all prephenate dehydrogenase activity when T-protein was expressed with 38 amino acids cut off at its C-terminus, but chorismate mutase and regulatory activity were both retained. It was concluded that chorismate mutase domain had an independent and compact structure, but prephenate dehydrogenase domain had a loose conformation interlaced with its regulatory domain.