PROBING INTERACTION OF MELITTIN WITH LIPID-MEMBRANES USING LIQUID SECONDARY-ION MASS-SPECTROMETRY

The membrane insertion mechanism of toxic protein is a very active dom ain in the study of molecular biology, and the ''anchor state'' of the membrane-hound protein on membrane is the key problem which it is dif ficult to solve with traditional methods. In the present work we first studied the ''anchor state'' of melittin on membrane using liquid sec ondary ion mass spectrometry (LSIMS) in combination with proteolysis b y specific enzyme. The results show that the membrane-bound melittin m olecules mainly lake the conformation in which the axis of a-helix lie s parallel to the membrane surface and the side containing LYS7, LYS21 and Arg(22) faces the outside of the lipid membrane. This discovery i s very significant to the studies of membrane insertion mechanism. The results also indicate that the combination of mass spectrometry techn ique with the proteolysis by specific enzyme has provided a very new a nd effective method for the studies of the membrane insertion mechanis m.