ABSTRACT
All ionotropic receptors and most ion channels are assembled
from several subunits arranged pseudo-symmetrically around a
central ion pore [reviewed in 1-10]. These protein complexes may
be either homomeric or heteromeric. In many (though not all)
cases, the total number of subunits within the protein complex
(the subunit stoichiometry) is known. However, the arrangement
of subunits within heteromeric complexes is often not known,
limiting our understanding of the relationship between structure
and function in both receptors and ion channels. In some cases, the
subunit arrangement is of therapeutic significance, since drugs are
known to bind at subunit-subunit interfaces. This is the case, for
example, with benzodiazepine binding to the gamma-aminobutyric
acid (GABAA) receptor [reviewed in 5], where an understanding of
the structure of the drug-binding site requires knowledge of which
subunits are adjacent to each other.
