title: MamK, a bacterial actin, forms dynamic filaments in vivo that are regulated by the acidic proteins MamJ and LimJ.
abstract: Bacterial actins, in contrast to their eukaryotic counterparts, are highly divergent proteins whose wide-ranging functions are thought to correlate with their evolutionary diversity. One clade, represented by the MamK protein of magnetotactic bacteria, is required for the subcellular organization of magnetosomes, membrane-bound organelles that aid in navigation along the earth's magnetic field. Using a fluorescence recovery after photobleaching assay in Magnetospirillum magneticum AMB-1, we find that, like traditional actins, MamK forms dynamic filaments that require an intact NTPase motif for their turnover in vivo. We also uncover two proteins, MamJ and LimJ, which perform a redundant function to promote the dynamic behaviour of MamK filaments in wild-type cells. The absence of both MamJ and LimJ leads to static filaments, a disrupted magnetosome chain, and an anomalous build-up of cytoskeletal filaments between magnetosomes. Our results suggest that MamK filaments, like eukaryotic actins, are intrinsically stable and rely on regulators for their dynamic behaviour, a feature that stands in contrast to some classes of bacterial actins characterized to date.
authors: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
authors: Olga
authors: O
authors: Draper
authors: Meghan E
authors: ME
authors: Byrne
authors: Zhuo
authors: Z
authors: Li
authors: Sepehr
authors: S
authors: Keyhani
authors: Joyce Cueto
authors: JC
authors: Barrozo
authors: Grant
authors: G
authors: Jensen
authors: Arash
authors: A
authors: Komeili
mesh_terms: D000199:Actins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D055944:Magnetosomes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D042201:Magnetospirillum / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment
chemical_list: D000199:Actins; D001426:Bacterial Proteins