Figure 2.

Proposed cationic patch classification of membrane lipid binding PDZ domains. The classification is based on positioning of the cationic patch as proposed by Chen et al. [44]. Class A domains do not display overlap of the protein and membrane lipid binding sites. The cationic patch is likely to be positioned opposite to the binding groove and/or involving the βE strand. Class B1 domains display proximal or partially overlapping protein- and membrane lipid-binding sites that may allosterically regulate each other. Often the cationic patch of class B1 domains involves residues C-terminal to the αA helix. Finally, the class B2 domains have overlapping protein- and lipid-binding sites and therefore class B2 domains will almost exclusive bind one or the other. A dashed black line delineates the binding pocket.