Otoda K, Kimura S, Imanishi Y
Department of Polymer Chemistry, Kyoto University, Japan.
Biochim Biophys Acta. 1992 Nov 23;1112(1):1-6. doi: 10.1016/0005-2736(92)90245-h.
Melittin possesses an amphiphilic property in the primary sequence in which hydrophilic residues are located at the C-terminal region from Lys-21 to Gln-26. A part of the hydrophilic sequence was cleaved off by endopeptidase Arg-C to obtain melittin 1-22. The affinity of melittin 1-22 for neutral phospholipid membrane was reduced to 1/3 that of melittin, indicating that the basic residues, Lys-23 and Arg-24, are important in binding of melittin to the membrane. The melittin 1-22 was extended toward the C-terminal end by connection of lactose (melittin-lac), the membrane affinity of which was slightly higher than the melittin 1-22, but lower than melittin. The leakage experiment of 5,6-carboxyfluorescein encapsulated in DPPC liposomes showed that the activities of melittin 1-22 and melittin-lac in membrane lysis were much lower than melittin. However, the melittin 1-22 formed a voltage-dependent ion-channel in an azolectin bilayer membrane. It is thus considered that Lys-23 and Arg-24 residues of melittin play an important role in binding to the polar region of membrane for lysis, but not for ion-channel formation.
蜂毒肽在其一级序列中具有两亲性，其中亲水残基位于从赖氨酸-21到谷氨酰胺-26的C末端区域。用内肽酶Arg-C切除亲水序列的一部分以获得蜂毒肽1-22。蜂毒肽1-22对中性磷脂膜的亲和力降低至蜂毒肽的1/3，这表明碱性残基赖氨酸-23和精氨酸-24在蜂毒肽与膜的结合中起重要作用。通过连接乳糖（蜂毒肽-乳糖）将蜂毒肽1-22向C末端延伸，其膜亲和力略高于蜂毒肽1-22，但低于蜂毒肽。对包裹在二棕榈酰磷脂酰胆碱脂质体中的5,6-羧基荧光素进行的泄漏实验表明，蜂毒肽1-22和蜂毒肽-乳糖在膜裂解中的活性远低于蜂毒肽。然而，蜂毒肽1-22在偶氮卵磷脂双层膜中形成了电压依赖性离子通道。因此可以认为，蜂毒肽的赖氨酸-23和精氨酸-24残基在与膜的极性区域结合以进行裂解方面起重要作用，但在离子通道形成方面不起作用。
