Srisucharitpanit Kanokporn, Yao Min, Promdonkoy Boonhiang, Chimnaronk Sarin, Tanaka Isao, Boonserm Panadda
Institute of Molecular Biosciences, Mahidol University, Salaya, Phuttamonthon, Nakhon Pathom, 73170, Thailand; Faculty of Allied Health Science, Burapha University, Saensook, Muang District, Chon Buri, 20131, Thailand.
Proteins. 2014 Oct;82(10):2703-12. doi: 10.1002/prot.24636. Epub 2014 Jul 5.
The binary toxin (Bin), produced by Lysinibacillus sphaericus, is composed of BinA (42 kDa) and BinB (51 kDa) proteins, which are both required for full toxicity against Culex and Anopheles mosquito larvae. Specificity of Bin toxin is determined by the binding of BinB component to a receptor present on the midgut epithelial membranes, while BinA is proposed to be a toxic component. Here, we determined the first crystal structure of the active form of BinB at a resolution of 1.75 Å. BinB possesses two distinct structural domains in its N- and C-termini. The globular N-terminal domain has a β-trefoil scaffold which is a highly conserved architecture of some sugar binding proteins or lectins, suggesting a role of this domain in receptor-binding. The BinB β-rich C-terminal domain shares similar three-dimensional folding with aerolysin type β-pore forming toxins, despite a low sequence identity. The BinB structure, therefore, is a new member of the aerolysin-like toxin family, with probably similarities in the cytolytic mechanism that takes place via pore formation.
球形赖氨酸芽孢杆菌产生的二元毒素（Bin）由BinA（42 kDa）和BinB（51 kDa）蛋白组成，这两种蛋白对于对库蚊和按蚊幼虫产生完全毒性都是必需的。Bin毒素的特异性由BinB组分与中肠上皮膜上存在的受体的结合决定，而BinA被认为是毒性组分。在此，我们以1.75 Å的分辨率确定了BinB活性形式的首个晶体结构。BinB在其N端和C端具有两个不同的结构域。球状的N端结构域具有β-三叶形支架，这是一些糖结合蛋白或凝集素的高度保守结构，表明该结构域在受体结合中起作用。尽管序列同一性较低，但富含β链的BinB C端结构域与气单胞菌溶素型β-孔形成毒素具有相似的三维折叠。因此，BinB结构是气单胞菌溶素样毒素家族的新成员，在通过孔形成发生的细胞溶解机制中可能具有相似性。
