Use of site‐directed antibodies to probe the topography of theα2 subunit of voltage‐gated Ca2+ channels

Abstract

Polyclonal antibodies were raised against peptides corresponding to residues 1–15, 469–483 and 933–951 of the rabbit skeletal muscle L‐type calcium channelα₂/δ primary translation product, for use as topological probes. Immunocytochemical comparison of the abilities of the antibodies to bind to theα₂ and δ 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 theα₂ subunit, and residues 1–17 of the δ subunit, are exposed on the extracellular surface of the membrane, findings consistent with a model that proposesα₂ to be entirely extracellular.