The Arabidopsis thaliana potassium channel KAT1 was expressed and characterized in Chinese hamster ovary cells. KAT1-GFP fusion protein was successfully targeted to the plasma membrane and electrophysiological analysis revealed functional expression of KAT1 only in cells cultured at 30 degrees C. The main biophysical characteristics of KAT1 are similar to those described for the channel expressed in other systems. CHO cells represent an advantageous expression system and may be the system of choice to study the expression, assembly, function, and regulation of plant potassium channels in general.