Chang Y F, Ma D P, Shi J, Chengappa M M
Diagnostic Laboratory, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853.
Infect Immun. 1993 May;61(5):2089-95. doi: 10.1128/iai.61.5.2089-2095.1993.
A Pasteurella haemolytica-like organism, a new species of bacterium isolated from piglets with diarrhea, secretes a leukotoxin into the culture media. Western blot (immunoblot) analysis indicated that this leukotoxin cross-reacted with antileukotoxin antibody derived from cattle immunized with P. haemolytica. Five overlapping recombinant bacteriophages carrying the gene for this 105-kDa polypeptide were identified with a DNA probe containing sequences from the P. haemolytica lktCA genes from a P. haemolytica-like organism strain 5943 genomic library. Sequence analysis of a region of the cloned DNA revealed two open reading frames encoding proteins with predicted masses of 19.4 and 101.6 kDa. These genes, which we designate pllktC (P. haemolytica-like organism leukotoxin C gene) and pllktA (A gene), respectively, are similar in sequence to the RTX (repeat of toxin) toxin family. The structure of the 101.6-kDa protein derived from the DNA sequence shows three transmembrane domains in the N-terminal part of the protein, 13 glycine-rich repeat domains in the second half of the protein, and a hydrophobic C-terminal part. pllktC and pllktA are strongly homologous to P. haemolytica lktC and lktA genes. However, this leukotoxin kills both BL-3 and pig leukocytes and is not hemolytic.
一种类溶血巴斯德氏菌，从患腹泻的仔猪中分离出的一种新型细菌，可向培养基中分泌一种白细胞毒素。蛋白质免疫印迹（免疫印迹）分析表明，这种白细胞毒素与用溶血巴斯德氏菌免疫的牛源抗白细胞毒素抗体发生交叉反应。用来自类溶血巴斯德氏菌菌株5943基因组文库的包含溶血巴斯德氏菌lktCA基因序列的DNA探针，鉴定出五个携带该105 kDa多肽基因的重叠重组噬菌体。对克隆DNA区域的序列分析揭示了两个开放阅读框，分别编码预测分子量为19.4 kDa和101.6 kDa的蛋白质。我们分别将这些基因命名为pllktC（类溶血巴斯德氏菌白细胞毒素C基因）和pllktA（A基因），它们在序列上与RTX（毒素重复序列）毒素家族相似。从DNA序列推导的101.6 kDa蛋白质的结构显示，该蛋白质N端部分有三个跨膜结构域，后半部分有13个富含甘氨酸的重复结构域，以及一个疏水的C端部分。pllktC和pllktA与溶血巴斯德氏菌lktC和lktA基因高度同源。然而，这种白细胞毒素既能杀死BL - 3细胞，也能杀死猪白细胞，且不具有溶血活性。
