Dervyn E, Poncet S, Klier A, Rapoport G
Unité de Biochimie Microbienne, Institut Pasteur, Unité de Recherche Associée 1300 du Centre National de la Recherche Scientifique, Paris, France.
J Bacteriol. 1995 May;177(9):2283-91. doi: 10.1128/jb.177.9.2283-2291.1995.
The CryIVD protein is involved in the overall toxicity of the Bacillus thuringiensis subsp. israelensis parasporal inclusions and is one of the four major components of the crystals. Determination of the DNA sequence indicated that the cryIVD gene is the second gene of an operon which includes three genes. The first one encodes a 19-kDa polypeptide and has sequence homology with the orf1 gene of the Bacillus thuringiensis cryIIA and cryIIC operons. The second and third genes have already been identified and encode the CryIVD crystal protein and the P20 polypeptide, respectively. The promoter region was located by deletion analysis, and the 5' end of the mRNA was determined by primer extension mapping. Transcription of the cryIVD gene in B. thuringiensis subsp. israelensis strains is induced 9 h after the beginning of sporulation. Sequence analysis indicated two potential promoters, a strong one and a weak one, recognized respectively by the RNA polymerase associated with the sigma 35 or the sigma 28 factor of B. thuringiensis (sigma E and sigma K of Bacillus subtilis, respectively). Transcriptional lacZ fusion integrated in single copy into the chromosome of various B. subtilis sporulation mutants confirmed the sigma E dependence of cryIVD gene transcription.
CryIVD蛋白与苏云金芽孢杆菌以色列亚种伴孢晶体的整体毒性有关，是晶体的四个主要成分之一。DNA序列测定表明，cryIVD基因是一个操纵子的第二个基因，该操纵子包含三个基因。第一个基因编码一种19 kDa的多肽，与苏云金芽孢杆菌cryIIA和cryIIC操纵子的orf1基因具有序列同源性。第二个和第三个基因已被鉴定，分别编码CryIVD晶体蛋白和P20多肽。通过缺失分析确定了启动子区域，并通过引物延伸图谱确定了mRNA的5'端。苏云金芽孢杆菌以色列亚种菌株中cryIVD基因的转录在芽孢形成开始后9小时被诱导。序列分析表明有两个潜在的启动子，一个强启动子和一个弱启动子，分别被与苏云金芽孢杆菌的σ35或σ28因子相关的RNA聚合酶识别（分别为枯草芽孢杆菌的σE和σK）。以单拷贝整合到各种枯草芽孢杆菌芽孢形成突变体染色体中的转录lacZ融合证实了cryIVD基因转录对σE的依赖性。
