Hormozi K, Parton R, Coote J
Division of Infection and Immunity, Glasgow University, UK.
FEMS Microbiol Lett. 1998 Dec 1;169(1):139-45. doi: 10.1111/j.1574-6968.1998.tb13310.x.
The leukotoxin (LktA) of Pasteurella haemolytica is active only against cells of ruminant origin. It is synthesised as an inactive protoxin encoded by the lktA gene and post-translationally modified to the active toxin by the product of the lktC gene. The LktA and LktC proteins were expressed separately in Escherichia coli and partially purified. Active LktA was produced in vitro in the presence of LktC and acyl-acyl carrier protein (ACP) charged separately in vitro with a fatty-acyl group. The toxic activity and target cell specificity of LktA and adenylate cyclase toxin (CyaA), a toxin active against a wide variety of mammalian cells, were investigated after activation with ACP charged with different fatty acids. Palmitoyl-ACP produced the most active toxin in both cases and, although other fatty acids were also effective, the fatty acid preference was the same for the in vitro activation of both toxins. Activated LktA remained ruminant cell-specific whichever acyl group was used to acylate the A protoxin.
溶血巴斯德菌的白细胞毒素（LktA）仅对反刍动物来源的细胞具有活性。它最初作为由lktA基因编码的无活性原毒素合成，经lktC基因产物进行翻译后修饰成为活性毒素。LktA和LktC蛋白分别在大肠杆菌中表达并部分纯化。活性LktA是在体外存在LktC以及分别在体外与脂肪酰基结合的酰基 - 酰基载体蛋白（ACP）的情况下产生的。在用带有不同脂肪酸的ACP激活后，研究了LktA和腺苷酸环化酶毒素（CyaA，一种对多种哺乳动物细胞具有活性的毒素）的毒性活性和靶细胞特异性。在这两种情况下，棕榈酰 - ACP产生的毒素活性最高，尽管其他脂肪酸也有效，但两种毒素体外激活的脂肪酸偏好相同。无论使用哪种酰基来酰化原毒素A，激活后的LktA仍具有反刍动物细胞特异性。
