Protein Domain : MPP5, SH3 domain IPR035601

Type	Domain
Description	MPP5, also called PALS1 (protein associated with Lin7) or Nagie oko protein in zebrafish [ ] or Stardust in Drosophila [], is a scaffolding protein which associates with Crumbs homologue 1 (CRB1), CRB2, or CRB3 through its PDZ domain and with PALS1-associated tight junction protein (PATJ) or multi-PDZ domain protein 1 (MUPP1) through its L27 domain []. The resulting tri-protein complexes are core proteins of the Crumb complex, which localizes at tight junctions or subapical regions, and is involved in the maintenance of apical-basal polarity in epithelial cells and the morphogenesis and function of photoreceptor cells []. MPP5 is critical for the proper stratification of the retina and is also expressed in T lymphocytes where it is important for TCR-mediated activation of NFkB []. Drosophila Stardust exists in several isoforms, some of which show opposing functions in photoreceptor cells, which suggests that the relative ratio of different Crumbs complexes regulates photoreceptor homeostasis []. MPP5 belongs to the membrane-associated guanylate kinase (MAGUK) p55 subfamily.The membrane-associated guanylate kinase (MAGUK) p55 subfamily (also known as MPP subfamily) members include the Drosophila Stardust protein and its vertebrate homologues, MPP1-7. They contain the core of three domains characteristic of MAGUK (membrane-associated guanylate kinase) proteins: PDZ, SH3, and guanylate kinase (GuK). In addition, they also contain the Hook (Protein 4.1 Binding) motif in between the SH3 and GuK domains [ ]. MPP2-7 have two additional L27 domains at their N terminus. The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain [].
Short Name	MPP5_SH3