Mörtl S, Fischer M, Richter G, Tack J, Weinkauf S, Bacher A
Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, D-85747 Garching, Federal Republic of Germany.
J Biol Chem. 1996 Dec 27;271(52):33201-7. doi: 10.1074/jbc.271.52.33201.
A gene located at 443 kilobases on the Escherichia coli chromosome (subsequently designated ribE) was expressed in a recombinant E. coli strain and was shown to code for the enzyme 6, 7-dimethyl-8-ribityllumazine synthase. The recombinant enzyme was purified to homogeneity. The protein is an icosahedral capsid of 60 subunits with a mass of about 1 MDa as shown by hydrodynamic studies and by electron microscopy. In contrast to the icosahedral lumazine synthase-riboflavin synthase complex of Bacillus subtilis, the lumazine synthase of E. coli is not physically associated with another enzyme of the riboflavin pathway, and the core of the icosahedral capsid is empty. The RIB4 gene of Saccharomyces cerevisiae was also expressed to a high level (about 40% of cellular protein) in E. coli. The recombinant protein is a pentamer of 90 kDa. An insertion of 4 amino acids into helix alpha4 is likely to hinder the formation of an icosahedral capsid by the yeast protein. The kinetic properties of lumazine synthase of E. coli, B. subtilis, and S. cerevisiae are similar.
位于大肠杆菌染色体上443千碱基处的一个基因（随后命名为ribE）在一株重组大肠杆菌菌株中表达，并被证明编码6,7-二甲基-8-核糖基芦竹碱合酶。重组酶被纯化至同质。如流体动力学研究和电子显微镜所示，该蛋白质是由60个亚基组成的二十面体衣壳，质量约为1兆道尔顿。与枯草芽孢杆菌的二十面体芦竹碱合酶-核黄素合酶复合物不同，大肠杆菌的芦竹碱合酶在物理上不与核黄素途径的另一种酶相关联，并且二十面体衣壳的核心是空的。酿酒酵母的RIB4基因在大肠杆菌中也高水平表达（约占细胞蛋白的40%）。重组蛋白是90 kDa的五聚体。在α4螺旋中插入4个氨基酸可能会阻碍酵母蛋白形成二十面体衣壳。大肠杆菌、枯草芽孢杆菌和酿酒酵母的芦竹碱合酶的动力学性质相似。
