Isolation of the [3H]gabapentin-binding protein/alpha 2 delta Ca2+ channel subunit from porcine brain: development of a radioligand binding assay for alpha 2 delta subunits using [3H]leucine

Anal Biochem. 1998 Jan 15;255(2):236-43. doi: 10.1006/abio.1997.2447.


The novel antiepileptic agent gabapentin (Neurontin) binds with high affinity to the alpha 2 delta subunit of a voltage-dependent Ca2+ channel. We report here a simple purification scheme for detergent-solubilized alpha 2 delta subunits from porcine brain. This involves sequential chromatography on Q-Sepharose, Cu(2+)-charged iminodiacetic acid-Sepharose, wheat germ lectin-agarose, and Mono Q. The purified protein was essentially homogeneous by SDS-polyacrylamide gel electrophoresis with a subunit Mr of 145,000. Using [3H] gabapentin as the radiolabeled tracer and (S)-3-isobutyl gamma-aminobutyric acid to define nonspecific binding, the overall purification factor was 2760-fold and the apparent yield 26.6%. We also developed and validated a novel binding assay for alpha 2 delta Ca2+ channel subunits using the ligand pair L-[3H]leucine/L-isoleucine. Even in binding assays of crude brain membrane fractions, [3H]leucine proved to be remarkably stable and specific for the alpha 2 delta Ca2+ channel subunit. [3H]Leucine offers several advantages over custom-labeled [3H]gabapentin: it has a higher specific activity, is relatively inexpensive, and is available from commercial sources.

MeSH terms

  • Acetates / metabolism*
  • Amines*
  • Animals
  • Calcium Channels / isolation & purification*
  • Calcium Channels / metabolism
  • Cerebral Cortex / chemistry
  • Cerebral Cortex / metabolism*
  • Chromatography, High Pressure Liquid
  • Cyclohexanecarboxylic Acids*
  • Gabapentin
  • Kinetics
  • Leucine / metabolism*
  • Macromolecular Substances
  • Neurons / chemistry
  • Protein Binding
  • Radioligand Assay
  • Swine
  • Tritium
  • gamma-Aminobutyric Acid*


  • Acetates
  • Amines
  • Calcium Channels
  • Cyclohexanecarboxylic Acids
  • Macromolecular Substances
  • Tritium
  • gamma-Aminobutyric Acid
  • Gabapentin
  • Leucine