蜂毒素与紫膜的相互作用机理研究──与三种表面活性剂的比较

THE MECHANISM OF INTERACTION OF MELITIN WITH PURPLE MEMBRANE ──COMPARED WITH THREE KINDS OF SURFACTANTS

用吸收光谱和圆二色谱的方法研究了蜂毒素与嗜血菌紫膜的相互作用机理．通过与三种在结构和电荷上不同的表面活性剂与紫膜的作用相比较，可以年出蜂毒作为带正电荷的分子与同样带正电的表面活性剂ＤＴＡＢ在引起紫膜凝聚方面表现相同；但在对紫膜可见光区的吸收光谱和圆二色谱的影响上却与具有刚性结构的ＣＨＡＰＳ相似，表明蜂毒可在紫膜表面以一种刚性较大的构象（如α螺旋）存在，不能进入膜蛋白流水区的深层．另外，从紫膜－Ｔｒｉｔｏｎ－蜂毒混合作用体系的研究中得到如下推测：蜂毒与Ｔｒｉｔｏｎ竞争菌紫质分子周围的结合位点，可排斥位于菌紫质周围的Ｔｒｉｔｏｎ分子．表明蜂毒具有比Ｔｒｉｔｏｎ更强的与菌紫质的亲和力，从而提供了支持蜂毒分子存在与膜蛋白－菌紫质的直接相互作用的有力证据．

Melittin of be venom has strong effects on purple membrane of H. halobium. It caused aggregation of purple membrane fragments at very low concentration. This effect might be attributed to its positive charges because cationic surfactant DTAB acted the same. On the other hand, melittin seemed to have behavior similar to CHAPS which has a rigid cholane ring,both had little effect on the conformation of retinal chromporphores.In consideration of the two-dimensional crystalline structure of purple membrane,melittin may form a rigid conformation such as α-helix on the surface of the membrane. In the study of action of melittin purple membrane solubilized in Triton X-100, a competition in scrambling for the binding cites of bacteriorhodopsin between melittin and Triton molecules was found.The spec tral results give direct evidence of the intrection between melittin and membrane protein.