title: Structural basis for small G protein effector interaction of Ras-related protein 1 (Rap1) and adaptor protein Krev interaction trapped 1 (KRIT1).
abstract: Cerebral cavernous malformations (CCMs) affect 0.1-0.5% of the population resulting in leaky vasculature and severe neurological defects. KRIT1 (Krev interaction trapped-1) mutations associate with ∼40% of familial CCMs. KRIT1 is an effector of Ras-related protein 1 (Rap1) GTPase. Rap1 relocalizes KRIT1 from microtubules to cell membranes to impact integrin activation, potentially important for CCM pathology. We report the 1.95 Å co-crystal structure of KRIT1 FERM domain in complex with Rap1. Rap1-KRIT1 interaction encompasses an extended surface, including Rap1 Switch I and II and KRIT1 FERM F1 and F2 lobes. Rap1 binds KRIT1-F1 lobe using a GTPase-ubiquitin-like fold interaction but binds KRIT1-F2 lobe by a novel interaction. Point mutagenesis confirms the interaction. High similarity between KRIT1-F2/F3 and talin is revealed. Additionally, the mechanism for FERM domains acting as GTPase effectors is suggested. Finally, structure-based alignment of each lobe suggests classification of FERM domains as ERM-like and TMFK-like (talin-myosin-FAK-KRIT-like) and that FERM lobes resemble domain "modules."
authors.affiliation: Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Li
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.forename: Kyle M
authors.initials: KM
authors.lastname: Draheim
authors.forename: Weizhi
authors.initials: W
authors.lastname: Liu
authors.forename: David A
authors.initials: DA
authors.lastname: Calderwood
authors.forename: Titus J
authors.initials: TJ
authors.lastname: Boggon
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray / Q000379:methods; D020558:GTP Phosphohydrolases / Q000378:metabolism; D005786:Gene Expression Regulation; D020786:Hemangioma, Cavernous, Central Nervous System / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000378:metabolism; D000075927:KRIT1 Protein; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D017354:Point Mutation; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D016023:Integrins; D000075927:KRIT1 Protein; C107928:KRIT1 protein, human; D008869:Microtubule-Associated Proteins; D011518:Proto-Oncogene Proteins; D020558:GTP Phosphohydrolases; D020827:rap1 GTP-Binding Proteins