Membrane-associated guanylate kinase (MAGUK) family members function as molecular scaffolds for the assembly of multiprotein complexes localizing to the plasma membrane. Several mammalian proteins related to the Drosophila tumor suppressor discs-large (dlg) gene product belong to the MAGUK family. MAGUK family members include the postsynaptic proteins PSD-93, PalS1, PSD-95 (SAP 90), densin-180, NE-dlg (SAP 120), dlg-1 (SAP 97), GKAP (GK-associated protein), p55, the tight junction associated proteins ZO-1-3 and the caspase-associated recruitment domain (CARD) proteins CARD11 and CARD14. Membrane-associated guanylate kinase inverted (MAGI) proteins MAGI-1-3 share a high degree of similarity with MAGUK proteins.