The low-affinity cation transporter (LCT1) from wheat (Triticum aestivum) was expressed in the methylotrophic yeast Pichia pastoris and its transport characteristics studied employing Ca-45 and Cd-109. A clone (LCTI#3) with the highest uptake of 14 pmol of Ca/10(6) cells/10 min when exposed to 100 mu M Ca-45 was chosen for further Ca-45 and Cd-109 transport characteristics. We report for the first time a K-m for Ca by LCT1 of 0.43 +/- 0.15 mM Ca activity which confirms LCT1 to be a low affinity transporter. Interestingly, the expression of LCT1 in Pichia resulted in reduced Cd-109 uptake compared to wild type cells, when cells were exposed to >= 60 mu M Cd. This is the first report of the ability of a heterologously expressed transporter to reduce the activity of endogenous transporter proteins to transport Cd. To our knowledge, this is the first demonstration of functional expression of a plant ion transporter using P. pastoris. (c) 2006 Elsevier Inc. All rights reserved.