title: In vitro assembly of the bacterial actin protein MamK from ' Candidatus Magnetobacterium casensis' in the phylum Nitrospirae.
abstract: Magnetotactic bacteria (MTB), a group of phylogenetically diverse organisms that use their unique intracellular magnetosome organelles to swim along the Earth's magnetic field, play important roles in the biogeochemical cycles of iron and sulfur. Previous studies have revealed that the bacterial actin protein MamK plays essential roles in the linear arrangement of magnetosomes in MTB cells belonging to the Proteobacteria phylum. However, the molecular mechanisms of multiple-magnetosome-chain arrangements in MTB remain largely unknown. Here, we report that the MamK filaments from the uncultivated 'Candidatus Magnetobacterium casensis' (Mcas) within the phylum Nitrospirae polymerized in the presence of ATP alone and were stable without obvious ATP hydrolysis-mediated disassembly. MamK in Mcas can convert NTP to NDP and NDP to NMP, showing the highest preference to ATP. Unlike its Magnetospirillum counterparts, which form a single magnetosome chain, or other bacterial actins such as MreB and ParM, the polymerized MamK from Mcas is independent of metal ions and nucleotides except for ATP, and is assembled into well-ordered filamentous bundles consisted of multiple filaments. Our results suggest a dynamically stable assembly of MamK from the uncultivated Nitrospirae MTB that synthesizes multiple magnetosome chains per cell. These findings further improve the current knowledge of biomineralization and organelle biogenesis in prokaryotic systems.
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Aihua
authors.initials: A
authors.lastname: Deng
authors.affiliation: Biogeomagnetism Group, Paleomagnetism and Geochronology Laboratory, Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Lin
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Nana
authors.initials: N
authors.lastname: Shi
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Wu
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Zhaopeng
authors.initials: Z
authors.lastname: Sun
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Qinyun
authors.initials: Q
authors.lastname: Sun
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Bai
authors.affiliation: Biogeomagnetism Group, Paleomagnetism and Geochronology Laboratory, Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China.
authors.forename: Yongxin
authors.initials: Y
authors.lastname: Pan
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China. wenty@im.ac.cn.
authors.forename: Tingyi
authors.initials: T
authors.lastname: Wen
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D001419:Bacteria / Q000145:classification / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D042201:Magnetospirillum / Q000145:classification / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D010802:Phylogeny; D013379:Substrate Specificity
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D009711:Nucleotides; D000255:Adenosine Triphosphate
keywords: MamK; Nitrospirae; assembly mechanism; bacterial actin; magnetotactic bacteria