title: Evidence for cooperative and domain-specific binding of the signal transducing adaptor molecule 2 (STAM2) to Lys63-linked diubiquitin.
abstract: As the upstream component of the ESCRT (endosomal sorting complexes required for transport) machinery, the ESCRT-0 complex is responsible for directing ubiquitinated membrane proteins to the multivesicular body pathway. ESCRT-0 is formed by two subunits known as Hrs (hepatocyte growth factor-regulated substrate) and STAM (signal transducing adaptor molecule), both of which harbor multiple ubiquitin-binding domains (UBDs). In particular, STAM2 possesses two UBDs, the VHS (Vps27/Hrs/Stam) and UIM (ubiquitin interacting motif) domains, connected by a 20-amino acid flexible linker. In the present study, we report the interactions of the UIM domain and VHS-UIM construct of STAM2 with monoubiquitin (Ub), Lys(48)- and Lys(63)-linked diubiquitins. Our results demonstrate that the UIM domain alone binds monoubiquitin, Lys(48)- and Lys(63)-linked diubiquitins with the same affinity and in the same binding mode. Interestingly, binding of VHS-UIM to Lys(63)-linked diubiquitin is not only avid, but also cooperative. We also show that the distal domain of Lys(63)-linked diubiquitin stabilizes the helical structure of the UIM domain and that the corresponding complex adopts a specific structural organization responsible for its greater affinity. In contrast, binding of VHS-UIM to Lys(48)-linked diubiquitin and monoubiquitin is not cooperative and does not show any avidity. These results may explain the better sorting efficiency of some cargoes polyubiquitinated with Lys(63)-linked chains over monoubiquitinated cargoes or those tagged with Lys(48)-linked chains.
authors.affiliation: Université de Lyon, CNRS, UMR 5280 Institut des Sciences Analytiques, 69622 Villeurbanne, France.
authors.forename: Anja
authors.initials: A
authors.lastname: Lange
authors.forename: Carlos
authors.initials: C
authors.lastname: Castañeda
authors.forename: Daniela
authors.initials: D
authors.lastname: Hoeller
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Lancelin
authors.forename: David
authors.initials: D
authors.lastname: Fushman
authors.forename: Olivier
authors.initials: O
authors.lastname: Walker
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008239:Lysine / Q000378:metabolism*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D056827:Endosomal Sorting Complexes Required for Transport; C491647:STAM2 protein, human; D025801:Ubiquitin; D008239:Lysine