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苏云金芽孢杆菌（B．t．）是一种革兰氏阳性菌，在芽孢形成过程中产生一种伴胞晶体蛋白，被称为δ─内毒素或杀虫晶体蛋白（ICP，Insecticidalprotein）。目前所发现的ICP的毒杀范围包括鳞翅目、双翅目、鞘翅目等的昆虫，是目前世界上应用最为广泛的生物杀剂。B．t．基因所编码的蛋白为一种碱溶性蛋白（ICP），典型的ICP由两个部分构成，N端的活性片断和C端的结构片断．活性片断由毒性区与细胞结合区组成。携带结构片断的ICP被称作原毒，它经昆虫中肠道的蛋白酶消化后，可产生有毒性的毒性肽。具体步骤是：原毒素进入昆虫消化道后，先溶解，然后被某些特定的蛋白酶水解，释放出毒性肽。激活后的活化毒性肽的细胞结合区可与昆虫中肠道的纹缘膜上的受体结合。有人认为该受体是细胞膜上的一种糖蛋白。活化毒性肽的毒性区作用于细胞膜，使细胞膜穿孔，破坏了细胞的渗透平衡，并最后引起细胞裂解使昆虫死亡。B．t．毒蛋白能否毒杀某类昆虫取决于两点：（1）B．t．毒蛋白能否在昆虫的消化道深解，不同种类昆虫的消化道环境不同，而类型不同的ICP正常水解所需环境不同；（2）昆虫的消化道细胞膜上是否存在特异性受体、是否能与对应的毒性肽结合。有资料表明：B．t．的毒性与毒性肽和昆虫中肠道细胞的受体的结合
Bacillus thuringiensis (B.t.) is a Gram-positive bacterium that produces a companion crystal protein during sporulation called delta-endotoxin or insecticidal protein (ICP). Currently, ICP poisoning is found to include insects such as Lepidoptera, Diptera and Coleoptera, and is currently the most widely used biocide in the world. B. t. The protein encoded by the gene is an alkali-soluble protein (ICP). The typical ICP consists of two parts: the N-terminal active fragment and the C-terminal structural fragment. The active fragment consists of a toxic region and a cell binding region. The ICP that carries the structural fragment is called the virulent, which, after digestion by the protease of the insect’s intestine, produces toxic, toxic peptides. Specific steps are: the original toxin into the digestive tract of insects, first dissolved, and then by some specific proteolytic hydrolysis, release of toxic peptides. The activated cell-binding region of the activated toxic peptide binds to the receptor on the enveloping membrane of the intestinal tract of insects. Some people think that the receptor is a glycoprotein on the cell membrane. The toxic regions of activated toxic peptides act on the cell membrane, perforating the cell membrane, disrupting the osmotic balance of the cells, and eventually causing cell lysis to kill the insect. B. t. Whether a poison protein can kill certain kinds of insects depends on two things: (1) B. t. Whether the toxic protein can be deeply resolved in the digestive tract of insects, the digestive tract environment of different species of insects is different, and the environment required for normal hydrolysis of different types of ICP is different; (2) Whether there is a specific receptor on the digestive tract cell membrane of insects, whether Can be combined with the corresponding toxic peptide. Data show that: B. t. Of toxicity to the receptors of toxic peptides and intestinal cells in insects