title: The RAC binding domain/IRSp53-MIM homology domain of IRSp53 induces RAC-dependent membrane deformation.
abstract: The concave surface of the crescent-shaped Bin-amphiphysin-Rvs (BAR) domain is postulated to bind to the cell membrane to induce membrane deformation of a specific curvature. The Rac binding (RCB) domain/IRSp53-MIM homology domain (IMD) has a dimeric structure that is similar to the structure of the BAR domain; however, the RCB domain/IMD has a "zeppelin-shaped" dimer. Interestingly, the RCB domain/IMD of IRSp53 possesses Rac binding, membrane binding, and actin filament binding abilities. Here we report that the RCB domain/IMD of IRSp53 induces membrane deformation independent of the actin filaments in a Rac-dependent manner. In contrast to the BAR domain, the RCB domain/IMD did not cause long tubulation of the artificial liposomes; however, the Rac binding domain caused the formation of small buds on the liposomal surface. When expressed in cells, the Rac binding domain induced outward protrusion of the plasma membrane in a direction opposite to that induced by the BAR domain. Mapping of the amino acids responsible for membrane deformation suggests that the convex surface of the Rac binding domain binds to the membrane in a Rac-dependent manner, which may explain the mechanism of the membrane deformation induced by the RCB domain/IMD.
authors.affiliation: Department of Biochemistry, Institute of Medical Science, the University of Tokyo, Shirokanedai, Minato-ku, Tokyo 108-8639, USA.
authors.forename: Shiro
authors.initials: S
authors.lastname: Suetsugu
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Murayama
authors.forename: Ayako
authors.initials: A
authors.lastname: Sakamoto
authors.forename: Kyoko
authors.initials: K
authors.lastname: Hanawa-Suetsugu
authors.forename: Azusa
authors.initials: A
authors.lastname: Seto
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Oikawa
authors.forename: Chiemi
authors.initials: C
authors.lastname: Mishima
authors.forename: Mikako
authors.initials: M
authors.lastname: Shirouzu
authors.forename: Tadaomi
authors.initials: T
authors.lastname: Takenawa
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008081:Liposomes; D008958:Models, Molecular; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
chemical_list: C119539:BAIAP2 protein, human; D008081:Liposomes; D009419:Nerve Tissue Proteins; D020744:rac GTP-Binding Proteins