title: MuB is an AAA+ ATPase that forms helical filaments to control target selection for DNA transposition.
abstract: MuB is an ATP-dependent nonspecific DNA-binding protein that regulates the activity of the MuA transposase and captures target DNA for transposition. Mechanistic understanding of MuB function has previously been hindered by MuB's poor solubility. Here we combine bioinformatic, mutagenic, biochemical, and electron microscopic analyses to unmask the structure and function of MuB. We demonstrate that MuB is an ATPase associated with diverse cellular activities (AAA+ ATPase) and forms ATP-dependent filaments with or without DNA. We also identify critical residues for MuB's ATPase, DNA binding, protein polymerization, and MuA interaction activities. Using single-particle electron microscopy, we show that MuB assembles into a helical filament, which binds the DNA in the axial channel. The helical parameters of the MuB filament do not match those of the coated DNA. Despite this protein-DNA symmetry mismatch, MuB does not deform the DNA duplex. These findings, together with the influence of MuB filament size on strand-transfer efficiency, lead to a model in which MuB-imposed symmetry transiently deforms the DNA at the boundary of the MuB filament and results in a bent DNA favored by MuA for transposition.
authors.affiliation: Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Naoko
authors.initials: N
authors.lastname: Mizuno
authors.forename: Marija
authors.initials: M
authors.lastname: Dramićanin
authors.forename: Michiyo
authors.initials: M
authors.lastname: Mizuuchi
authors.forename: Julia
authors.initials: J
authors.lastname: Adam
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.forename: Yong-Woon
authors.initials: YW
authors.lastname: Han
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.forename: Alasdair C
authors.initials: AC
authors.lastname: Steven
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Mizuuchi
authors.forename: Santiago
authors.initials: S
authors.lastname: Ramón-Maiques
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D010583:Bacteriophage mu / Q000201:enzymology* / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D004279:DNA, Viral / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D021621:Imaging, Three-Dimensional; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D055503:Protein Multimerization / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D019895:Transposases / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D004279:DNA, Viral; D004268:DNA-Binding Proteins; C069215:MuB protein, Enterobacteria phage Mu; D014764:Viral Proteins; D000255:Adenosine Triphosphate; D019895:Transposases; D000251:Adenosine Triphosphatases
keywords: Phage Mu; nucleoprotein filament