Journal Article

The voltage-gated Na super(+) channel Na sub(V)BP has a role in motility, chemotaxis, and pH homeostasis of an alkaliphilic Bacillus

Clapham, David E, Zvi, Lior, Ito, Masahiro, Krulwich, Terry A, Wei, Yi, Xu, Haoxing, Guffanti, Arthur A

2004

Overview

The prokaryotic voltage-gated Na super(+) channel, NaChBac, is one of a growing channel superfamily of unknown function. Here we show that Na sub(V)BP, the NaChBac homologue encoded by ncbA in alkaliphilic Bacillus pseudofirmus OF4, is a voltage-gated Na super(+) channel potentiated by alkaline pH. Na sub(V)BP has roles in motility, chemotaxis, and pH homeostasis at high pH. Reduced motility of bacteria lacking functional Na sub(V)BP was reversed by restoration of the native channel but not by a mutant Na sub(V)BP engineered to be Ca super(2+)-selective. Motile ncbA mutant cells and wild-type cells treated with a channel inhibitor exhibited behavior opposite to the wild type in response to chemoeffectors. Mutants lacking functional Na sub(V)BP were also defective in pH homeostasis in response to a sudden alkaline shift in external pH under conditions in which cytoplasmic [Na super(+)] is limiting for this crucial process. The defect was exacerbated by mutation of motPS, the motility channel genes. We hypothesize that activation of Na sub(V)BP at high pH supports diverse physiological processes by a combination of direct and indirect effects on the Na super(+) cycle and the chemotaxis system.

• Subject: Bacillus pseudofirmus