Steiner H, Hultmark D, Engström A, Bennich H, Boman H G
Nature. 1981 Jul 16;292(5820):246-8. doi: 10.1038/292246a0.
Immune responses have been described for many different insect species. However, it is generally acknowledged that immune systems must therefore differ from those of vertebrates. An effective humoral immune response has been found in pupae of the cecropia moth, Hyalophora cecropia. The expression of this multicomponent system requires de novo synthesis of RNA and proteins and its broad antibacterial activity is due to at least three independent mechanisms, the most well known of which is the insect lysozyme. However, this enzyme is bactericidal for only a limited number of Gram-positive bacteria. WE recently purified and characterized P9A and P9B, which are two small, basic proteins with potent antibacterial activity against Escherichia coli and several other Gram-negative bacteria. We believe that P9A and P9B plays an important part in the humoral immune responses described previously and that the P9 proteins represent a new class of antibacterial agents for which we propose the name cecropins. We describe here the primary structures of cecropins A and B. We also show that cecropin A is specific for bacteria in contrast to melittin, the main lytic component in bee venom which lyses both bacteria and eukaryotic cells.
许多不同昆虫物种的免疫反应已被描述。然而，人们普遍认为，昆虫的免疫系统必然与脊椎动物的免疫系统不同。在天蚕蛾（大透目天蚕蛾）的蛹中发现了一种有效的体液免疫反应。这种多组分系统的表达需要RNA和蛋白质的从头合成，其广泛的抗菌活性至少归因于三种独立机制，其中最著名的是昆虫溶菌酶。然而，这种酶仅对有限数量的革兰氏阳性菌具有杀菌作用。我们最近纯化并鉴定了P9A和P9B，它们是两种小的碱性蛋白质，对大肠杆菌和其他几种革兰氏阴性菌具有强大的抗菌活性。我们认为P9A和P9B在先前描述的体液免疫反应中起重要作用，并且P9蛋白代表了一类新的抗菌剂，我们将其命名为杀菌肽。我们在此描述了杀菌肽A和B的一级结构。我们还表明，与蜂毒中的主要裂解成分蜂毒肽不同，杀菌肽A对细菌具有特异性，蜂毒肽既能裂解细菌也能裂解真核细胞。
