Franklin S E, Young L, Watson D, Cigan A, Meyer T, Bulla L A
Department of Molecular Biology, University of Wyoming, Laramie 82071, USA.
Mol Gen Genet. 1997 Nov;256(5):517-24. doi: 10.1007/s004380050596.
Various subspecies of the gram-positive bacterium Bacillus thuringiensis are known to produce a wide array of insecticidal crystal proteins (ICPs) upon sporulation. These ICPs act primarily on the brush border of midgut epithelial cells of susceptible larvae. Recently, a protein of 210 kDa, isolated from the midgut of Manduca sexta, has been demonstrated to bind the Cry1Ab toxin produced by B. thuringiensis subsp, berliner and is therefore postulated to be involved in mediating the toxicity of Cry1Ab. The cDNA encoding the 210 kDa protein, termed BT-R1 (Bacillus thuringiensis receptor-1), was recently cloned, and shows limited homology to the cadherin superfamily of proteins. Quite naturally, there is a great deal of interest in the characterization of BT-R1, the gene encoding the 210 kDa Cry1Ab binding protein. The studies presented here involve the use of various restriction fragments prepared from the cDNA encoding BT-R1 as probes of Southern blots bearing M. sexta genomic DNA cleaved with a variety of restriction endonucleases. These Southern blot data reveal that there are two discrete regions within the M. sexta genome which encode sequences homologous to BT-R1. On the basis of the signal intensities seen on Southern blots, it appears that only one of these genes encodes BT-R1, whereas the other is a closely related homologue.
已知革兰氏阳性细菌苏云金芽孢杆菌的各种亚种在形成芽孢时会产生多种杀虫晶体蛋白（ICP）。这些ICP主要作用于易感幼虫中肠上皮细胞的刷状缘。最近，从烟草天蛾中肠分离出的一种210 kDa的蛋白质已被证明能结合苏云金芽孢杆菌亚种berliner产生的Cry1Ab毒素，因此推测它参与介导Cry1Ab的毒性。编码这种210 kDa蛋白质的cDNA，称为BT - R1（苏云金芽孢杆菌受体 - 1），最近已被克隆，并且与钙黏蛋白超家族的蛋白质具有有限的同源性。自然而然地，人们对BT - R1（编码210 kDa Cry1Ab结合蛋白的基因）的特性有极大的兴趣。本文介绍的研究涉及使用从编码BT - R1的cDNA制备的各种限制性片段作为Southern印迹的探针，该Southern印迹带有用多种限制性内切酶切割的烟草天蛾基因组DNA。这些Southern印迹数据表明，烟草天蛾基因组中有两个离散区域编码与BT - R1同源的序列。根据Southern印迹上观察到的信号强度，似乎这些基因中只有一个编码BT - R1，而另一个是密切相关的同源物。
