FIGURE 1.

Calneuron-1 is a transmembrane protein. A, schematic representation of calneuron-1 (Caln1) in the membrane-inserted form. The functional EF-hands 1 and 2 are depicted in green, and the cryptic EF-hands 3 and 4 are depicted in red. The green circle represents the EGFP tag fused to the N or C terminus of the protein. In live staining experiments, the fluorophore (magenta circle)-tagged antibody can bind only to the extracellularly exposed antigen. B, COS-7 cells transfected with EGFP-calneuron-1 or calneuron-1-EGFP were subjected to live staining with the rabbit anti-GFP antibody for 1 h at 37 °C. Only the cells transfected with calneuron-1-EGFP show immunoreactivity with the GFP antibody, indicating that the tag is extracellular. Scale bar, in B is 10 μm.