title: Insights regarding guanine nucleotide exchange from the structure of a DENN-domain protein complexed with its Rab GTPase substrate.
abstract: Rab GTPases are key regulators of membrane traffic pathways within eukaryotic cells. They are specifically activated by guanine nucleotide exchange factors (GEFs), which convert them from their "inactive" GDP-bound form to the "active" GTP-bound form. In higher eukaryotes, proteins containing DENN-domains comprise a major GEF family. Here we describe at 2.1-Å resolution the first structure of a DENN-domain protein, DENND1B-S, complexed with its substrate Rab35, providing novel insights as to how DENN-domain GEFs interact with and activate Rabs. DENND1B-S is bi-lobed, and interactions with Rab35 are through conserved surfaces in both lobes. Rab35 binds via switch regions I and II, around the nucleotide-binding pocket. Positional shifts in Rab residues required for nucleotide binding may lower its affinity for bound GDP, and a conformational change in switch I, which makes the nucleotide-binding pocket more solvent accessible, likely also facilitates exchange.
authors: Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
authors: Xudong
authors: X
authors: Wu
authors: Michael J
authors: MJ
authors: Bradley
authors: Yiying
authors: Y
authors: Cai
authors: Daniel
authors: D
authors: Kümmel
authors: Enrique M
authors: EM
authors: De La Cruz
authors: Francis A
authors: FA
authors: Barr
authors: Karin M
authors: KM
authors: Reinisch
mesh_terms: D001665:Binding Sites; D001692:Biological Transport; D018360:Crystallography, X-Ray / Q000379:methods; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D009711:Nucleotides / Q000737:chemistry; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020691:rab GTP-Binding Proteins / Q000737:chemistry*; D020761:rab1 GTP-Binding Proteins / Q000737:chemistry
chemical_list: C546321:DENND1B protein, human; D053418:Death Domain Receptor Signaling Adaptor Proteins; D020662:Guanine Nucleotide Exchange Factors; D009711:Nucleotides; D006147:Guanine; C511183:RAB35 protein, human; C529587:Rab1B protein, human; D020691:rab GTP-Binding Proteins; D020761:rab1 GTP-Binding Proteins