HPLC and MS Studies of Orientation of Melittin on Phospholipid Membrane

The orientation of melittin binding to liposomes with or without transmembrane potential was investigated. With a combination of high performance liquid chromatography and mass spectrometry, the membrane association state of melittin was detected by analyzing its trypsin-digested products. It was found that the enzyme could access all the proteolytic sites on protein binding to the liposome without membrane potential, while one proteolytic site on the N-terminal of the protein was blocked after it binding to the liposome with negative transmembrane potential. The results showed that melittin changed its orientation in the latter case.