Koni P A, Ellar D J
Department of Biochemistry, University of Cambridge, England.
J Mol Biol. 1993 Jan 20;229(2):319-27. doi: 10.1006/jmbi.1993.1037.
A gene encoding a major entomocidal polypeptide from Bacillus thuringiensis subspecies kyushuensis delta-endotoxin crystals (CytB) was cloned into Escherichia coli and sequenced. The deduced amino acid sequence gave a predicted molecular mass of 29,236 Da and showed 39% identity and 70% similarity with the 27,371 Da CytA protein from Bacillus thuringiensis subspecies israelensis. The larger size of CytB compared to CytA appears to be due to additional sequence in CytB after the CytA C-terminus. Unlike CytA, CytB was freely expressed in Escherichia coli and formed cytoplasmic inclusions without the need for a "helper" protein. Electron microscopic observation of CytB inclusions revealed them to be generally amorphous, but examples possessing some lattice structure were seen.
编码来自苏云金芽孢杆菌九州亚种δ-内毒素晶体（CytB）的一种主要杀昆虫多肽的基因被克隆到大肠杆菌中并进行了测序。推导的氨基酸序列预测分子量为29,236道尔顿，与来自苏云金芽孢杆菌以色列亚种的27,371道尔顿的CytA蛋白具有39%的同一性和70%的相似性。与CytA相比，CytB的较大尺寸似乎是由于CytB在CytA C末端之后有额外的序列。与CytA不同，CytB在大肠杆菌中可自由表达并形成细胞质内含物，无需“辅助”蛋白。对CytB内含物的电子显微镜观察显示它们通常是无定形的，但也观察到了一些具有某种晶格结构的例子。
