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MamK, a bacterial actin, forms dynamic filaments in vivo that are regulated by the acidic proteins MamJ and LimJ
Author(s) -
Draper Olga,
Byrne Meghan E.,
Li Zhuo,
Keyhani Sepehr,
Barrozo Joyce Cueto,
Jensen Grant,
Komeili Arash
Publication year - 2011
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2011.07815.x
Subject(s) - magnetosome , magnetotactic bacteria , fluorescence recovery after photobleaching , biology , organelle , cytoskeleton , actin , microbiology and biotechnology , subcellular localization , cytoplasm , biophysics , bacteria , biochemistry , membrane , genetics , cell
Summary 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.