Escherichia coli as an expression system for K⁺ transport systems from plants

The value of the Escherichia coli expression system has long been established because of its effectiveness in characterizing the structure and function of exogenously expressed proteins. When eukaryotic membrane proteins are functionally expressed in E. coli, this organism can serve as an alternative to eukaryotic host cells. A few examples have been reported of functional expression of animal and plant membrane proteins in E. coli. This mini-review describes the following findings: 1) homologous K⁺ transporters exist in prokaryotic cells and in eukaryotic cells; 2) plant K⁺ transporters can functionally complement mutant K⁺ transporter genes in E. coli; and 3) membrane structures of plant K⁺ transporters can be elucidated in an E. coli system. These experimental findings suggest the possibility of utilizing the E. coli bacterium as an expression system for other eukaryotic membrane transport proteins.