However, the mechanism by which this bacterium secretes glutamate remains unclear.
It was reported that a mutation in NCgl1221 results in spontaneous glutamate secretion, and disruption of this gene essentially inhibits glutamate secretion.
NCgl1221 encodes a homolog of the mechanosensitive channel of small conductance (MscS).
In this study, we used an electrophysical technique to analyze the functions of this protein in Bacillus subtilis cell expressing the NCgl1221.
B. subtilis possesses 4 genes encoding mechanosensitive channel homologs. Therefore, mscL, ykuT, yhdY and yfkC quadruple–disruptant strain of B. subtilis was constructed; further, a C. glutamicum gene (NCgl1221) was expressed under the control of xylose promoter.
Our findings showed that the giant provacuole prepared from the quadruple -disruptant strain of B. subtilis, expressing Ncgl1221, showed significantly higher pressure-dependent conductance in the buffer containing L-glutamic acid.
The same tendency had founded even if it changed glutamic acid into aspartic acid.
This data suggest that the NCgl1221 encodes a mechanosensitive channel, and this channel was activated by responding to membrane tension.
The glutamic acid and aspartic acid could be secreted by this channel along concentration gradient.