Interaction of the MARCKS peptide with PIP2 in phospholipid monolayers

In this present work we have studied the effect of MARCKS (151–175) peptide on a mixed DPPC/PIP₂ monolayer. By means of film balance, fluorescence microscopy, x-ray reflection/diffraction and neutron reflection measurements we detected changes in the lateral organization of the monolayer and changes in the perpendicular orientation of the PIP₂ molecules depending on the presence of MARCKS (151–175) peptide in the subphase. In the mixed monolayer, the PIP₂ molecules are distributed uniformly in the disordered phase of the monolayer, whereas the PI(4,5) groups elongate up to 10 Å below the phosphodiester groups. This elongation forms the precondition for the electrostatic interaction of the MARCKS peptide with the PIP₂ molecules. Due to the enrichment of PIP₂ in the disordered phase, the interaction with the peptide occurs primarily in this phase, causing the PI(4,5) groups to tilt toward the monolayer interface.