title: Structure of the magnetosome-associated actin-like MamK filament at subnanometer resolution.
abstract: Magnetotactic bacteria possess cellular compartments called magnetosomes that sense magnetic fields. Alignment of magnetosomes in the bacterial cell is necessary for their function, and this is achieved through anchoring of magnetosomes to filaments composed of the protein MamK. MamK is an actin homolog that polymerizes upon ATP binding. Here, we report the structure of the MamK filament at ∼6.5 Å, obtained by cryo-Electron Microscopy. This structure confirms our previously reported double-stranded, nonstaggered architecture, and reveals the molecular basis for filament formation. While MamK is closest in sequence to the bacterial actin MreB, the longitudinal contacts along each MamK strand most closely resemble those of eukaryotic actin. In contrast, the cross-strand interface, with a surprisingly limited set of contacts, is novel among actin homologs and gives rise to the nonstaggered architecture.
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, Washington.
authors.forename: Julien R C
authors.initials: JR
authors.lastname: Bergeron
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, Washington.
authors.forename: Rachel
authors.initials: R
authors.lastname: Hutto
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California.
authors.forename: Ertan
authors.initials: E
authors.lastname: Ozyamak
authors.affiliation: Department of Medicinal Chemistry, University of Washington, Seattle, Washington.
authors.forename: Nancy
authors.initials: N
authors.lastname: Hom
authors.affiliation: Department of Biochemistry, University of British Columbia, Vancouver, British Columbia.
authors.forename: Jesse
authors.initials: J
authors.lastname: Hansen
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California.
authors.forename: Olga
authors.initials: O
authors.lastname: Draper
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California.
authors.forename: Meghan E
authors.initials: ME
authors.lastname: Byrne
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California.
authors.forename: Sepehr
authors.initials: S
authors.lastname: Keyhani
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California.
authors.forename: Arash
authors.initials: A
authors.lastname: Komeili
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, Washington.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Kollman
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism / Q000648:ultrastructure*; D055944:Magnetosomes / Q000378:metabolism / Q000648:ultrastructure*; D042201:Magnetospirillum / Q000378:metabolism / Q000648:ultrastructure*; D046912:Multiprotein Complexes / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D001426:Bacterial Proteins; D046912:Multiprotein Complexes
keywords: Cryo-EM; actin; filaments; magnetosome