title: Overall Shapes of the SMC-ScpAB Complex Are Determined by Balance between Constraint and Relaxation of Its Structural Parts.
abstract: The SMC-ScpAB complex plays a crucial role in chromosome organization and segregation in many bacteria. It is composed of a V-shaped SMC dimer and an ScpAB subcomplex that bridges the two Structural Maintenance of Chromosomes (SMC) head domains. Despite its functional significance, the mechanistic details of SMC-ScpAB remain obscure. Here we provide evidence that ATP-dependent head-head engagement induces a lever movement of the SMC neck region, which might help to separate juxtaposed coiled-coil arms. Binding of the ScpA N-terminal domain (NTD) to the SMC neck region is negatively regulated by the ScpB C-terminal domain. Mutations in the ScpA NTD compromise this regulation and profoundly affect the overall shape of the complex. The SMC hinge domain is structurally relaxed when free from coiled-coil juxtaposition. Taken together, we propose that the structural parts of SMC-ScpAB are subjected to the balance between constraint and relaxation, cooperating to modulate dynamic conformational changes of the whole complex.
authors.affiliation: Chromosome Dynamics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. Electronic address: kamadak@riken.jp.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kamada
authors.affiliation: Department of Life Science, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Su'etsugu
authors.affiliation: Department of Life Science, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501, Japan.
authors.forename: Hiraku
authors.initials: H
authors.lastname: Takada
authors.affiliation: Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Miyata
authors.affiliation: Chromosome Dynamics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Hirano
mesh_terms: D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D055503:Protein Multimerization
chemical_list: D018797:Cell Cycle Proteins
keywords: ATPase; Bacillus subtilis; Condensin; SMC; ScpA; ScpB; chromosome organization; segregation