SPECIFICITY OF BACILLUS-THURINGIENSIS DELTA-ENDOTOXINS - IMPORTANCE OF SPECIFIC RECEPTORS ON THE BRUSH-BORDER MEMBRANE OF THE MID-GUT OF TARGET INSECTS
SPECIFICITY OF BACILLUS-THURINGIENSIS DELTA-ENDOTOXINS - IMPORTANCE OF SPECIFIC RECEPTORS ON THE BRUSH-BORDER MEMBRANE OF THE MID-GUT OF TARGET INSECTS
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DOI：
10.1111/j.1432-1033.1989.tb15201.x
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发表时间：
1989-12-01
期刊：
影响因子：
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通讯作者：
VANMELLAERT, H
中科院分区：
文献类型：
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作者：
VANRIE, J;JANSENS, S;VANMELLAERT, H
为了研究苏云金芽孢杆菌δ-内毒素杀虫谱差异的分子基础，我们用三种δ-内毒素对来自幼虫中肠的膜制备物进行了结合研究。通过详细研究125 I标记的Bt 2毒素（一种重组B）的结合，建立了标准结合试验的条件。苏云金杆菌δ-内毒素对烟草天蛾刷状缘膜囊泡的毒性与苏云金杆菌δ-内毒素相当。平衡结合研究显示，在烟芽夜蛾的刷状缘膜囊泡上有可饱和的高亲和力结合位点。SextaandH.绿色的三种毒素对H的亲和力无显著差异。在病毒囊泡中，结合位点浓度存在显著差异，反映了体内毒性的差异，竞争实验显示结合位点的异质性。为H。virescens，提出了一个三位点模型。InM. sexta中，一个群体的结合位点是由所有三种毒素共享的，而另一个群体仅被Bt3毒素识别。其他几种毒素，无毒或毒性小得多。Sextathan Bt 2毒素不能或仅少量取代125 I标记的Bt 2毒素在该昆虫中的结合。这些数据提供了新的证据，表明与肠上皮细胞膜上的特异性受体结合是B的杀虫谱差异的重要决定因素。苏云金芽孢杆菌晶体蛋白。
To study the molecular basis of differences in the insecticidal spectrum ofBacillus thuringiensisδ‐endotoxins, we have performed binding studies with three δ‐endotoxins on membrane preparations from larval insect midgut. Conditions for a standard binding assay were established through a detailed study of the binding of125I‐labeled Bt2 toxin, a recombinantB. thuringiensisδ‐endotoxin, to brush border membrane vesicles ofManduca sexta.The toxins tested (Bt2, Bt3 and Bt73 toxins) are about equally toxic toM. sextabut differ in their toxicity againstHeliothis virescens.Equilibrium binding studies revealed saturable, high‐affinity binding sites on brush border membrane vesicles ofM. sextaandH. virescens. While the affinity of the three toxins was not significantly different onH. virescensvesicles, marked differences in binding site concentration were measured which reflected the differences inin vivotoxicity.Competition experiments revealed heterogeneity in binding sites. ForH. virescens, a three‐site model was proposed. InM. sexta, one population of binding sites is shared by all three toxins, while another is only recognized by Bt3 toxin. Several other toxins, non‐toxic or much less toxic toM. sextathan Bt2 toxin, did not or only marginally displace binding of125I‐labeled Bt2 toxin in this insect. No saturable binding of this toxin was observed to membrane preparations from tissues of several non‐susceptible organisms.Together, these data provide new evidence that binding to a specific receptor on the membrane of gut epithelial cells is an important determinant with respect to differences in insecticidal spectrum ofB. thuringiensisinsecticidal crystal proteins.