USE OF SITE-DIRECTED ANTIBODIES TO PROBE THE TOPOGRAPHY OF THE ALPHA(2) SUBUNIT OF VOLTAGE-GATED CA2+ CHANNELS

Polyclonal antibodies were raised against peptides corresponding to residues 1-15, 469-483 and 933-951 of the rabbit skeletal muscle L-type calcium channel alpha(2)/delta primary translation product, for use as topological probes. Immunocytochemical comparison of the abilities of the antibodies to bind to the alpha(2) and delta subunits in intact and detergent-permeabilised rat dorsal root ganglion cells enabled the membrane orientation of these regions to be established. The resultant data indicate that the regions containing residues 1-15 and 469-483 of the alpha(2) subunit, and residues 1-17 of the delta subunit, are exposed on the extracellular surface of the membrane, findings consistent with a model that proposes alpha(2) to be entirely extracellular.