We and our collaborators have been using the gene regulatory systems and the resistance proteins to develop biosensors for heavy metals. Two types of biosensors have been produced. The first puts the lux genes of Vibrio fischeri under the control of the metal-regulated promoter, and the amount of bioavailable metal is measured from the amount of light emitted due to expression of the lux gene products. Such gene-based biosensors are sensitive and specific. The second type of biosensor uses the metal resistance proteins themselves, immobilised on the surface of an electrode.
Metal binding by the protein is transduced into a capacitance change.
We have investigated the properties of such electrodes. Differential binding of the metals can be detected at both low and high concentrations and the shape of the binding curves may be related to the biological roles of the proteins. These electrodes may not show sufficient discrimination between metals to be useful for environmental samples, but could be very useful for laboratory studies of metal binding to proteins.