Low-affinity potassium transporter. Could mediate the potassium-dependent cell expansion in growing tissues. Slightly detected in roots, stems, leaves and flowers of mature plants and in potassium-starved plants. Localized to cotyledons and hypocotyl in the early stages of development, and later appears in young leaves. Plants display a short hypocotyl phenotype. Kup2-2, kup2-3 and kup2-7 are considered as null mutants. Belongs to the HAK/KUP transporter (TC 2.A.72.3) family.