title: The N-terminal domain of MuB protein has striking structural similarity to DNA-binding domains and mediates MuB filament-filament interactions.
abstract: MuB is an ATP-dependent DNA-binding protein that regulates the activity of MuA transposase and delivers the target DNA for transposition of phage Mu. Mechanistic insight into MuB function is limited to its AAA+ ATPase module, which upon ATP binding assembles into helical filaments around the DNA. However, the structure and function of the flexible N-terminal domain (NTD) appended to the AAA+ module remains uncharacterized. Here we report the solution structure of MuB NTD determined by NMR spectroscopy. The structure reveals a compact domain formed by four α-helices connected by short loops, and confirms the presence of a helix-turn-helix motif. High structural similarity and sequence homology with λ repressor-like DNA-binding domains suggest a possible role of MuB NTD in DNA binding. We also demonstrate that the NTD directly mediates the ability of MuB to establish filament-filament interactions. These findings lead us to a model in which the NTD interacts with the AAA+ spirals and perhaps also with the DNA bound within the filament, favoring MuB polymerization and filament clustering. We propose that the MuB NTD-dependent filament interactions might be an effective mechanism to bridge distant DNA regions during Mu transposition.
authors.affiliation: Structural Bases of Genome Integrity Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fdez. Almagro, 3, Madrid 28029, Spain.
authors.forename: Marija
authors.initials: M
authors.lastname: Dramićanin
authors.affiliation: Spectroscopy and Nuclear Magnetic Resonance Unit, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fdez. Almagro, 3, Madrid 28029, Spain.
authors.forename: Blanca
authors.initials: B
authors.lastname: López-Méndez
authors.affiliation: Electron Microscopy Unit, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fdez. Almagro, 3, Madrid 28029, Spain.
authors.forename: Jasminka
authors.initials: J
authors.lastname: Boskovic
authors.affiliation: Spectroscopy and Nuclear Magnetic Resonance Unit, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fdez. Almagro, 3, Madrid 28029, Spain.
authors.forename: Ramón
authors.initials: R
authors.lastname: Campos-Olivas
authors.affiliation: Structural Bases of Genome Integrity Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fdez. Almagro, 3, Madrid 28029, Spain. Electronic address: sramon@cnio.es.
authors.forename: Santiago
authors.initials: S
authors.lastname: Ramón-Maiques
mesh_terms: D001665:Binding Sites; D004247:DNA / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000737:chemistry*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D014764:Viral Proteins / Q000737:chemistry*
chemical_list: D004268:DNA-Binding Proteins; C069215:MuB protein, Enterobacteria phage Mu; D014764:Viral Proteins; D004247:DNA
keywords: Helix-turn-helix; NMR structure; Phage Mu; Transposition immunity; λ repressor-like