title: Interplay between two bacterial actin homologs, MamK and MamK-Like, is required for the alignment of magnetosome organelles in Magnetospirillum magneticum AMB-1.
abstract: Many bacterial species contain multiple actin-like proteins tasked with the execution of crucial cell biological functions. MamK, an actin-like protein found in magnetotactic bacteria, is important in organizing magnetosome organelles into chains that are used for navigation along geomagnetic fields. MamK and numerous other magnetosome formation factors are encoded by a genetic island termed the magnetosome island. Unlike most magnetotactic bacteria, Magnetospirillum magneticum AMB-1 (AMB-1) contains a second island of magnetosome-related genes that was named the magnetosome islet. A homologous copy of mamK, mamK-like, resides within this islet and encodes a protein capable of filament formation in vitro. Previous work had shown that mamK-like is expressed in vivo, but its function, if any, had remained unknown. Though MamK-like is highly similar to MamK, it contains a mutation that in MamK and other actins blocks ATPase activity in vitro and filament dynamics in vivo. Here, using genetic analysis, we demonstrate that mamK-like has an in vivo role in assisting organelle alignment. In addition, MamK-like forms filaments in vivo in a manner that is dependent on the presence of MamK and the two proteins interact in a yeast two-hybrid assay. Surprisingly, despite the ATPase active-site mutation, MamK-like is capable of ATP hydrolysis in vitro and promotes MamK filament turnover in vivo. Taken together, these experiments suggest that direct interactions between MamK and MamK-like contribute to magnetosome alignment in AMB-1.
authors: Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA.
authors: Nicole
authors: N
authors: Abreu
authors: CEA, IBEB, Lab Bioenerget Cellulaire, Saint-Paul-lez-Durance, France CNRS, UMR Biol Veget & Microbiol Environ, Saint-Paul-lez-Durance, France Aix-Marseille Université, Saint-Paul-lez-Durance, France.
authors: Soumaya
authors: S
authors: Mannoubi
authors: Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA.
authors: Ertan
authors: E
authors: Ozyamak
authors: CEA, IBEB, Lab Bioenerget Cellulaire, Saint-Paul-lez-Durance, France CNRS, UMR Biol Veget & Microbiol Environ, Saint-Paul-lez-Durance, France Aix-Marseille Université, Saint-Paul-lez-Durance, France.
authors: David
authors: D
authors: Pignol
authors: CEA, IBEB, Lab Bioenerget Cellulaire, Saint-Paul-lez-Durance, France CNRS, UMR Biol Veget & Microbiol Environ, Saint-Paul-lez-Durance, France Aix-Marseille Université, Saint-Paul-lez-Durance, France.
authors: Nicolas
authors: N
authors: Ginet
authors: Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA komeili@berkeley.edu.
authors: Arash
authors: A
authors: Komeili
mesh_terms: D000199:Actins / Q000737:chemistry*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D055944:Magnetosomes / Q000502:physiology*; D042201:Magnetospirillum / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D000251:Adenosine Triphosphatases