FIGURE 3.

Electrostatic interactions are important for the Pyd PDZ2-membrane interaction. A, homology model of dimeric Pyd PDZ2 (subunits in green and cyan ribbons) with residues probed by mutagenesis shown in a blue stick representation (see Table 2). Residues numbered in black indicate mutations that resulted in significant loss of lipid binding and membrane localization, whereas residues marked in gray indicate mutations with only minor effects. Asterisks indicate mutations that also caused loss of peptide binding. B, equipotential contour plot of the calculated electrostatic potential of Pyd PDZ2, visualized by drawing meshes for the values +1 kT/e (25 mV, blue mesh) and −1 kT/e (−25 mV, red mesh) outside the molecular surface of the protein. C, fluorescent confocal micrographs of eYFP-Pyd PDZ2 mutants in MCF-7 cells. Note that all mutations except R201A and R244A resulted in complete loss of membrane targeting.