Spatial Localizations of Mam22 and Mam12 in the Magnetosomes of
            <i>Magnetospirillum magnetotacticum</i>

Taoka, Azuma; Asada, Ryuji; Sasaki, Hideaki; Anzawa, Kazushi; Wu, Long‐Fei; Fukumori, Yoshihiro

doi:10.1128/jb.00020-06

Cited by 70 publications

(82 citation statements)

References 23 publications

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“…A mutant strain harbouring the defected gene encoding this protein showed lesser BacMP formation in comparison with its wild-type counterpart, suggesting that the protein may be required for the activation of BacMP vesicles (Komeili et al 2004). Taoka et al (2006) recently reported the presence of a novel matrix surrounding a chain of BacMPs. They investigated the precise localization of Mam22 and Mam12 (identical to Mms13 and MamC) and revealed that Mam22 and Mam12 exist in the matrix and the BacMP membrane, respectively.…”

Section: Protein Analyses Of the Bacmp Membranementioning

confidence: 99%

Formation of magnetite by bacteria and its application

Arakaki

Nakazawa

Nemoto

et al. 2008

J. R. Soc. Interface.

219

176

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Magnetic particles offer high technological potential since they can be conveniently collected with an external magnetic field. Magnetotactic bacteria synthesize bacterial magnetic particles (BacMPs) with well-controlled size and morphology. BacMPs are individually covered with thin organic membrane, which confers high and even dispersion in aqueous solutions compared with artificial magnetites, making them ideal biotechnological materials. Recent molecular studies including genome sequence, mutagenesis, gene expression and proteome analyses indicated a number of genes and proteins which play important roles for BacMP biomineralization. Some of the genes and proteins identified from these studies have allowed us to express functional proteins efficiently onto BacMPs, through genetic engineering, permitting the preservation of the protein activity, leading to a simple preparation of functional protein-magnetic particle complexes. They were applicable to high-sensitivity immunoassay, drug screening and cell separation. Furthermore, fully automated single nucleotide polymorphism discrimination and DNA recovery systems have been developed to use these functionalized BacMPs. The nano-sized fine magnetic particles offer vast potential in new nano-techniques.

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Section: Protein Analyses Of the Bacmp Membranementioning

confidence: 99%

Formation of magnetite by bacteria and its application

Arakaki

Nakazawa

Nemoto

et al. 2008

J. R. Soc. Interface.

219

176

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“…The 12.4-kDa MamC protein, which is the most abundant MMP, was shown to be resistant against solubilization by weak detergents and is tightly associated with the MM (10), probably owing to its two predicted transmembrane segments. Immunogold staining has shown that in M. magnetotacticum, MamC localizes exclusively in the MM (36). The second most abundant protein identified in MM preparations from M. gryphiswaldense is the 12.3-kDa MamF protein, which contains three predicted transmembrane segments and tends to form stable oligomers even in the presence of sodium dodecyl sulfate (9).…”

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confidence: 99%

“…The hydrophobic proteins MamD (30.2 kDa) and MamG (7.7 kDa) are partially identical and share a conspicuous motif containing a Leu-Gly-dipeptide repeat, which is reminiscent of repetitive sequences found in self-aggregating framework proteins (6,34,41). Based on their abundance in the MM, their exclusive occurrence in MTB, and their high level of conservation, MamC and the further gene products of the mamGFDC operon have been suggested to play a key role in magnetite crystal formation (29,36,40). However, until the present study, their specific functions in magnetosome formation have remained completely elusive.…”

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confidence: 99%

The Major Magnetosome Proteins MamGFDC Are Not Essential for Magnetite Biomineralization inMagnetospirillum gryphiswaldensebut Regulate the Size of Magnetosome Crystals

et al. 2008

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Magnetospirillum gryphiswaldense and related magnetotactic bacteria form magnetosomes, which are membrane-enclosed organelles containing crystals of magnetite (Fe 3 O 4 ) that cause the cells to orient in magnetic fields. The characteristic sizes, morphologies, and patterns of alignment of magnetite crystals are controlled by vesicles formed of the magnetosome membrane (MM), which contains a number of specific proteins whose precise roles in magnetosome formation have remained largely elusive. Here, we report on a functional analysis of the small hydrophobic MamGFDC proteins, which altogether account for nearly 35% of all proteins associated with the MM. Although their high levels of abundance and conservation among magnetotactic bacteria had suggested a major role in magnetosome formation, we found that the MamGFDC proteins are not essential for biomineralization, as the deletion of neither mamC, encoding the most abundant magnetosome protein, nor the entire mamGFDC operon abolished the formation of magnetite crystals. However, cells lacking mamGFDC produced crystals that were only 75% of the wild-type size and were less regular than wild-type crystals with respect to morphology and chain-like organization. The inhibition of crystal formation could not be eliminated by increased iron concentrations. The growth of mutant crystals apparently was not spatially constrained by the sizes of MM vesicles, as cells lacking mamGFDC formed vesicles with sizes and shapes nearly identical to those formed by wild-type cells. However, the formation of wild-type-size magnetite crystals could be gradually restored by in-trans complementation with one, two, and three genes of the mamGFDC operon, regardless of the combination, whereas the expression of all four genes resulted in crystals exceeding the wild-type size. Our data suggest that the MamGFDC proteins have partially redundant functions and, in a cumulative manner, control the growth of magnetite crystals by an as-yet-unknown mechanism.The ability of magnetotactic bacteria (MTB) to orient in the earth's magnetic field is based on specific organelles, the magnetosomes, which are membrane-enveloped crystals of a magnetic mineral that are arranged in chain-like structures within the cell (5). Magnetosome crystals display a variety of species-specific shapes and sizes, which for most MTB are between 35 and 120 nm (3, 4). In MTB of the genus Magnetospirillum, cubo-octahedral nanocrystals of the magnetic mineral magnetite (Fe 3 O 4 ) are synthesized within magnetosome membrane (MM) vesicles, which are roughly spherical and are formed by invagination from the cytoplasmic membrane prior to magnetite biomineralization (2, 15, 16). The MM is a phospholipid bilayer with a distinctive biochemical composition (8,29,35). In Magnetospirillum gryphiswaldense, a specific set of 20 MM proteins (MMPs) was identified by biochemical and proteomic approaches (9,10,22), and these proteins were speculated to be involved in magnetosome biomineralization (29). However, the individual functions of M...

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“…Cellular localization analyses of magnetosome proteins were investigated using transmission electron microscopy (TEM) (26,27), atomic force microscopy (28), and fluorescence microscopy (29). Fluorescence microscopy is conventionally used with fluorescent-tagged protein-expressing transformants to analyze target protein localization behaviors in living magnetotactic bacteria.…”

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confidence: 99%

Comparative Subcellular Localization Analysis of Magnetosome Proteins Reveals a Unique Localization Behavior of Mms6 Protein onto Magnetite Crystals

et al. 2016

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The magnetosome is an organelle specialized for inorganic magnetite crystal synthesis in magnetotactic bacteria. The complex mechanism of magnetosome formation is regulated by magnetosome proteins in a stepwise manner. Protein localization is a key step for magnetosome development; however, a global study of magnetosome protein localization remains to be conducted. Here, we comparatively analyzed the subcellular localization of a series of green fluorescent protein (GFP)-tagged magnetosome proteins. The protein localizations were categorized into 5 groups (short-length linear, middle-length linear, long-length linear, cell membrane, and intracellular dispersing), which were related to the protein functions. Mms6, which regulates magnetite crystal growth, localized along magnetosome chain structures under magnetite-forming (microaerobic) conditions but was dispersed in the cell under nonforming (aerobic) conditions. Correlative fluorescence and electron microscopy analyses revealed that Mms6 preferentially localized to magnetosomes enclosing magnetite crystals. We suggest that a highly organized spatial regulation mechanism controls magnetosome protein localization during magnetosome formation in magnetotactic bacteria. IMPORTANCEMagnetotactic bacteria synthesize magnetite (Fe 3 O 4 ) nanocrystals in a prokaryotic organelle called the magnetosome. This organelle is formed using various magnetosome proteins in multiple steps, including vesicle formation, magnetosome alignment, and magnetite crystal formation, to provide compartmentalized nanospaces for the regulation of iron concentrations and redox conditions, enabling the synthesis of a morphologically controlled magnetite crystal. Thus, to rationalize the complex organelle development, the localization of magnetosome proteins is considered to be highly regulated; however, the mechanisms remain largely unknown. Here, we performed comparative localization analysis of magnetosome proteins that revealed the presence of a spatial regulation mechanism within the linear structure of magnetosomes. This discovery provides evidence of a highly regulated protein localization mechanism for this bacterial organelle development. P rotein localization at appropriate positions within a cell is an essential mechanism for the effective performance of the diverse biological reactions that occur within the restricted intracellular area in both eukaryotes and prokaryotes. In various prokaryotes, intracellular compartments can be created to provide the domains required for highly specialized reactions. Whereas some of these compartments are completely proteinaceous (e.g., carboxysomes, metabolosomes, and ferritin) (1-3), others contain molecular components similar to those in cell membranes, including lipids and proteins (e.g., nucleoids, polyhydroxybutyrate, and spores) (4, 5). Such compartmentalized organelles are recognized to be formed within bacteria through multiple processes involving the spatial regulation of protein localization, but the details of this regulatory m...

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Spatial Localizations of Mam22 and Mam12 in the Magnetosomes of Magnetospirillum magnetotacticum

Cited by 70 publications

References 23 publications

Formation of magnetite by bacteria and its application

Formation of magnetite by bacteria and its application

The Major Magnetosome Proteins MamGFDC Are Not Essential for Magnetite Biomineralization inMagnetospirillum gryphiswaldensebut Regulate the Size of Magnetosome Crystals

Comparative Subcellular Localization Analysis of Magnetosome Proteins Reveals a Unique Localization Behavior of Mms6 Protein onto Magnetite Crystals

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