Haider M Z, Mahmood S
Department of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan.
J Basic Microbiol. 1990;30(4):251-8. doi: 10.1002/jobm.3620300406.
Bacillus thuringiensis strains produce crystal delta-endotoxins which exhibit a diverse toxicity spectrum. In order to explore the basis of toxin specificity, a comparison of the activity of 13 strains belonging to seven serotypes was made against three insect species. The delta-endotoxin crystals were purified and their polypeptide composition analyzed by SDS-PAGE. Among the strains studied, the delta-endotoxins consist of a variety of crystal proteins in the 60-144 KDa size range. On the basis of molecular mass, endotoxins maybe grouped into two classes; one contained both high (125-144 KDa, P1) and medium sized (60-66 KDa, P2) proteins and a second class consisting of only the high Mr polypeptides. Immunoblotting with B. aizawai P1 antiserum revealed antigenic cross-reaction with one or more of the polypeptides in 125-144 KDa range in all the strains studied. When the crystal proteins from different strains were immunoblotted with kurstaki P2 antiserum, none of the P1 protein crossreacted suggesting that the P1 and P2 proteins are not structurally related. However, the B. kurstaki P2 antiserum crossreacted with 66 KDa proteins in some other strains which underlines a structural homology in this class of the toxic polypeptides. Toxicity studies revealed that the high Mr P1 proteins of all the strains in this study were active against lepidopteran (Pieris brassicae and Diacrisia obliqua) larvae. B. thuringiensis aizawai strains exhibit a dual toxicity associated with the high Mr (130-135 KDa; P1) proteins. The P2 crystal proteins (60-66 KDa) also showed dual toxicity against the lepidopteran and dipteran larvae but were found to be structurally and immunologically distinct.
苏云金芽孢杆菌菌株产生的晶体δ-内毒素具有多样的毒性谱。为了探究毒素特异性的基础，对属于七个血清型的13个菌株针对三种昆虫的活性进行了比较。纯化了δ-内毒素晶体，并通过SDS-PAGE分析其多肽组成。在所研究的菌株中，δ-内毒素由分子量在60 - 144 kDa范围内的多种晶体蛋白组成。基于分子量，内毒素可分为两类；一类包含高分子量（125 - 144 kDa，P1）和中等分子量（60 - 66 kDa，P2）的蛋白，另一类仅由高分子量多肽组成。用苏云金芽孢杆菌 aizawai P1抗血清进行免疫印迹分析显示，在所研究的所有菌株中，125 - 144 kDa范围内的一种或多种多肽存在抗原交叉反应。当用库斯塔克氏亚种P2抗血清对不同菌株的晶体蛋白进行免疫印迹分析时，没有P1蛋白发生交叉反应，这表明P1和P2蛋白在结构上不相关。然而，库斯塔克氏亚种P2抗血清与其他一些菌株中的66 kDa蛋白发生了交叉反应，这突出了这类有毒多肽的结构同源性。毒性研究表明，本研究中所有菌株的高分子量P1蛋白对鳞翅目（粉纹夜蛾和斜纹夜蛾）幼虫具有活性。苏云金芽孢杆菌aizawai菌株表现出与高分子量（130 - 135 kDa；P1）蛋白相关联的双重毒性活性。P2晶体蛋白（60 - 66 kDa）对鳞翅目和双翅目幼虫也表现出双重毒性，但在结构和免疫方面是不同的。
