Interaction of melittin derivatives with lipid bilayer membrane. Role of basic residues at the C-terminal and their replacement with lactose.
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.
Otoda
K
K
Department of Polymer Chemistry, Kyoto University, Japan.
Kimura
S
S
Imanishi
Y
Y
D000595:Amino Acid Sequence; D007473:Ion Channels; D007785:Lactose / Q000737:chemistry*; D008051:Lipid Bilayers; D008081:Liposomes; D008555:Melitten / Q000378:metabolism*; D008969:Molecular Sequence Data; D010743:Phospholipids / Q000378:metabolism*; D013379:Substrate Specificity
D007473:Ion Channels; D008051:Lipid Bilayers; D008081:Liposomes; D010743:Phospholipids; D008555:Melitten; D007785:Lactose