Surface biotinylation of heteromeric Kv1 concatemers expressed in CHO cells. Concatenated constructs of Kv1.1-1.2 or Kv1.1-1.2-1.2-1.2 (Akhtar et al., 2002) were expressed CHO cells by electroporation of RNA transcripts from a Semliki Forest virus vector. After 48 h, electroporated cells were harvested in PBS buffer containing 5 mM EDTA. Cell surface biotinylation was performed with sulfo-NHS-LC-biotin (Pierce Chemical Co.), as recommended by the manufacturer. Membrane proteins solubilized with 2% Triton X-100 were precipitated using streptavidin-agarose (Pierce Chemical Co.). Bound proteins were dissolved in lithium dodecyl sulfate sample buffer (Invitrogen) and SDS-PAGE and Western blotting with anti-Kv1.2 antibody were performed, as outlined elsewhere (Akhtar et al., 2002). Lanes: 1, biotinylated Kv1.1-1.2; 2, total extract from cells expressing Kv1.1-1.2; 3, biotinylated Kv1.1-1.2-1.2-1.2; and 4, total extract from cells expressing Kv1.1-1.2-1.2-1.2.