Nature 1994 Aug 25;3706491:655-8. doi: 10.1038/370655a0.

Structure and transport mechanism of a high-affinity potassium uptake transporter from higher plants.

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Potassium is the most abundant cation in higher plants and is crucial for plant nutrition, growth, tropisms, enzyme homeostasis and osmoregulation. K+ accumulation can be rate-limiting for agricultural production. K+ uptake from soils into roots is largely mediated by high-affinity K+ uptake (Km approximately 10-40 microM) (refs 1, 2, 5-7). But although K+ channels allow low-affinity K+ uptake, both the transport mechanism and structure of the high-affinity K+ nutrition pathway remain unknown. Here we use expression cloning to isolate a complementary DNA encoding a membrane protein (HKT1) from wheat roots which confers the ability to take up K+. The substrate affinity, saturation and cation selectivity of HKT1 correspond to hallmark properties of classical high-affinity K+ uptake in plants. The transport mechanism of HKT1 uses K(+)-H+ co-uptake. Expression of HKT1 is localized to specific root and leaf regions which represent primary sites for K+ uptake in plants. HKT1 is important for plant nutrition and could possibly contribute to environmental alkali metal toxicities.

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