Figure 1.

(A) NIS secondary structure model. Putative rat NIS topology is shown as predicted on the basis of amino acid sequence (6). The 12 putative transmembrane domains are indicated by rectangles. Potential N-linked glycosylation sites are indicated by boldface asterisks. The C terminus region against which the anti-NIS Ab was generated is shaded. (B) Immunoblot analysis of FRTL-5 membranes with anti-NIS Ab. FRTL-5 and FRT membranes were isolated, electrophoresed, and electrotransferred onto nitrocellulose as described. Immunoblot analysis with anti-NIS Ab was conducted as described. Lanes 1 and 2, total FRTL-5 membranes (≈20 μg); lanes 3 and 4, FRTL-5 Na₂CO₃ (pH 11) extracted membranes (≈20 μg); lane 5, FRT total membranes (≈20 μg). Lanes 2 and 4 had 100 μg of peptide present during incubation with anti-NIS Ab. (C) Membrane vesicles were prepared from FRT and FRTL-5 cells and assayed as described (11). Shown is a time course of iodide uptake in membrane vesicles from FRTL-5 (□) and FRT cells (⋄) done in the presence of Na⁺. Points indicate average of triplicate determinations.