Western immunoblot analysis of the expression of WT and mutant maxi-K channels in lipid rafts from mouse fibroblasts. Sucrose density gradient centrifugation of 1% Triton X-100 solubilized extracts from transfected Ltk- cells were examined by Western blot analysis. Samples range from lowest density at left (lane 1) to highest density at right (lane 10). The (A) WT (B) mutant F1012A, and (C) mutant Y1007A, F1012A forms of the maxi-K channel (as indicated by boxed regions in panels on left) co-fractionate with caveolin-1 in low-density fractions (cav-1; right). However the (D) mutant Y1007A, F1012A, Y1015A form (visible at left) was not present in these low-density caveolin-associated fractions. Data shown are representative examples from 10 independent experiments for each protein form.