Zhang Lianhui, Xu Jinling, Birch Robert G
Department of Botany, The University of Queensland, Brisbane QLD 4072, Australia.
Microbiology (Reading). 1998 Feb;144 ( Pt 2):555-559. doi: 10.1099/00221287-144-2-555.
Albicidins are a family of phytotoxins and antibiotics which play an important role in the pathogenesis of sugarcane leaf scald disease. The albA gene from Klebsiella oxytoca encodes a protein which inactivates albicidin by heat-reversible binding. Albicidin ligand binding to a recombinant AlbA protein, purified by means of a glutathione S-transferase gene fusion system, is an almost instant and saturable reaction. Kinetic and stoichiometric analysis of the binding reaction indicated the presence of a single high affinity binding site with a dissociation constant of 6.4 x 10(-8) M. The AlbA-albicidin complex is stable from 4 to 40 degrees C, from pH 5 to 9 and in high salt solutions. Treatment with protein denaturants released all bound albicidin. These properties indicate that AlbA may be a useful affinity matrix for selective purification of albicidin antibiotics. AlbA does not bind to p-nitrophenyl butyrate or alpha-naphthyl butyrate, the substrates of the albicidin detoxification enzyme AlbD from Pantoea dispersa. The potential exists to pyramid genes for different mechanisms in transgenic plants to protect plastid DNA replication from inhibition by albicidins.
杀白菌素是一类植物毒素和抗生素，在甘蔗叶烧病的发病机制中起重要作用。来自产酸克雷伯菌的albA基因编码一种通过热可逆结合使杀白菌素失活的蛋白质。通过谷胱甘肽S-转移酶基因融合系统纯化的重组AlbA蛋白与杀白菌素配体的结合是一个几乎瞬间且可饱和的反应。结合反应的动力学和化学计量分析表明存在一个单一的高亲和力结合位点，解离常数为6.4×10⁻⁸ M。AlbA-杀白菌素复合物在4至40℃、pH 5至9以及高盐溶液中稳定。用蛋白质变性剂处理会释放所有结合的杀白菌素。这些特性表明AlbA可能是用于选择性纯化杀白菌素抗生素的有用亲和基质。AlbA不与分散泛菌的杀白菌素解毒酶AlbD的底物对硝基苯基丁酸酯或α-萘基丁酸酯结合。在转基因植物中，存在将不同机制的基因叠加起来以保护质体DNA复制免受杀白菌素抑制的潜力。
