The voltage-gated Na+ channel NaVBP co-localizes with methyl-accepting chemotaxis protein at cell poles of alkaliphilic Bacillus pseudofirmus OF4.
Na(V)BP, found in alkaliphilic Bacillus pseudofirmus OF4, is a member of the bacterial voltage-gated Na(+) channel superfamily. The alkaliphile requires Na(V)BP for normal chemotaxis responses and for optimal pH homeostasis during a shift to alkaline conditions at suboptimally low Na(+) concentrations. We hypothesized that interaction of Na(V)BP with one or more other proteins in vivo, specifically methyl-accepting chemotaxis proteins (MCPs), is involved in activation of the channel under the pH conditions that exist in the extremophile and could underpin its role in chemotaxis; MCPs transduce chemotactic signals and generally localize to cell poles of rod-shaped cells. Here, immunofluorescence microscopy and fluorescent protein fusion studies showed that an alkaliphile protein (designated McpX) that cross-reacts with antibodies raised against Bacillus subtilis McpB co-localizes with Na(V)BP at the cell poles of B. pseudofirmus OF4. In a mutant in which Na(V)BP-encoding ncbA is deleted, the content of McpX was close to the wild-type level but McpX was significantly delocalized. A mutant of B. pseudofirmus OF4 was constructed in which cheAW expression was disrupted to assess whether this mutation impaired polar localization of McpX, as expected from studies in Escherichia coli and Salmonella, and, if so, whether Na(V)BP would be similarly affected. Polar localization of both McpX and Na(V)BP was decreased in the cheAW mutant. The results suggest interactions between McpX and Na(V)BP that affect their co-localization. The inverse chemotaxis phenotype of ncbA mutants may result in part from MCP delocalization.
Graduate School of Life Sciences, Toyo University, Oura-gun, Gunma 374-0193, Japan.
Shun
S
Fujinami
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima, Yokosuka 237-0061, Japan.
Takako
T
Sato
Department of Pharmacology, School of Medicine, University of California, Davis, CA 95616, USA.
James S
JS
Trimmer
Howard Hughes Medical Institute, Department of Cardiovascular Research, Children's Hospital and Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
Benjamin W
BW
Spiller
Howard Hughes Medical Institute, Department of Cardiovascular Research, Children's Hospital and Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
David E
DE
Clapham
Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, NY 10029, USA.
Terry A
TA
Krulwich
Department of Frontier Bioscience, Faculty of Engineering, Hosei University 3-7-2 Kajino-cho, Koganei, Tokyo 184-8584, Japan.
Ikuro
I
Kawagishi
Graduate School of Life Sciences, Toyo University, Oura-gun, Gunma 374-0193, Japan.
Masahiro
M
Ito
D001407:Bacillus / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D016764:Cell Polarity; D002633:Chemotaxis; D015964:Gene Expression Regulation, Bacterial; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000378:metabolism*; D000072236:Methyl-Accepting Chemotaxis Proteins; D008856:Microscopy, Fluorescence; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism*
D001426:Bacterial Proteins; C485182:Cyan Fluorescent Protein; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D011993:Recombinant Fusion Proteins; D015222:Sodium Channels; D049452:Green Fluorescent Proteins