Localization and function of K⁺channels from tobacco cells

Abstract

We have isolated the gene encoding K⁺ channel from tobacco cells (Nicotiana tabacum cv. SR1). The gene products rescued the E. coli mutant defective in K⁺ uptake transport, but did not restore the growth of the K⁺-uptake-deficient yeast strain. Likewise, we could not find the K⁺ current when the gene was expressed in Xenopus laeivs oocytes. To determine the location of the K⁺ channel expression at the subcellular levels, the immunoblotting detection has been performed. A single band corresponding to the deduced molecular mass was seen in the tonoplast fraction, suggesting that the channel is located in the tonoplast. Thus we used plant or yeast expression system to measure the K⁺ channel current in the vacuole membrane. Compared with the currents of the non-transformed cells, the cells expressing the gene gave the K⁺ channel-mediated K⁺ currents. The K⁺ transport activity was dependent on the change of pH.