title: Crystal structure of the ubiquitin binding domains of rabex-5 reveals two modes of interaction with ubiquitin.
abstract: The interaction between ubiquitinated proteins and intracellular proteins harboring ubiquitin binding domains (UBDs) is critical to a multitude of cellular processes. Here, we report that Rabex-5, a guanine nucleotide exchange factor for Rab5, binds to Ub through two independent UBDs. These UBDs determine a number of properties of Rabex-5, including its coupled monoubiquitination and interaction in vivo with ubiquitinated EGFRs. Structural and biochemical characterization of the UBDs of Rabex-5 revealed that one of them (MIU, motif interacting with ubiquitin) binds to Ub with modes superimposable to those of the UIM (ubiquitin-interacting motif):Ub interaction, although in the opposite orientation. The other UBD, RUZ (Rabex-5 ubiquitin binding zinc finger) binds to a surface of Ub centered on Asp58(Ub) and distinct from the "canonical" Ile44(Ub)-based surface. The two binding surfaces allow Ub to interact simultaneously with different UBDs, thus opening new perspectives in Ub-mediated signaling.
authors.affiliation: IFOM, the FIRC Institute for Molecular Oncology Foundation, Via Adamello 16, 20139 Milan, Italy.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Penengo
authors.forename: Marina
authors.initials: M
authors.lastname: Mapelli
authors.forename: Andrea G
authors.initials: AG
authors.lastname: Murachelli
authors.forename: Stefano
authors.initials: S
authors.lastname: Confalonieri
authors.forename: Laura
authors.initials: L
authors.lastname: Magri
authors.forename: Andrea
authors.initials: A
authors.lastname: Musacchio
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Di Fiore
authors.forename: Simona
authors.initials: S
authors.lastname: Polo
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Schneider
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D004815:Epidermal Growth Factor / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D046912:Multiprotein Complexes; C108382:RABGEF1 protein, human; D025801:Ubiquitin; D004815:Epidermal Growth Factor