STRUCTURE AND FUNCTION OF MAMMALIAN POTASSIUM CHANNELS

The functions of potassium channels are central to the properties of all
excitable mammalian cells. Electrophysiological and pharmacokinetic
studies have defined many different classes of potassium channels.
However, the molecular basis of this diversity, and the relationships
between channel structure and function remain unknown. Through the use of
molecular cloning and electrophysiology, we have isolated, characterized,
and expressed in frog oocytes a mammalian potassium channel from rat
hippocampus. Surprisingly, the properties of this channel do not fit any
single kind of channel as defined by classical methods. The major goal of the research proposed here is to further our
understanding of the molecular basis of variations among the different
classes of mammalian potassium channels. First, we will clone,
characterize, and express in frog oocytes mammalian potassium channels,
both voltage and ligand gated, with distinct structural and functional
properties. The different kinds of channels will be compared to those
known by classical methods. Second, structure-function studies, using site
directed mutagenesis, will be performed using a range of potassium
channels with distinct properties. Site directed mutant studies of whole,
reconstructed channels will be conducted in oocytes. Third, ancillary
factors which may influence channel functions will be investigated.
Fourth, subunit-specific probes will be generated, based on established
nucleotide sequences, and employed in in situ hybridization studies to map
the expression patterns of potassium channels in the brain. By studying the structure and function of mammalian potassium channels in
this way, we hope to answer questions regarding the molecular basis of
potassium channel diversity and the significance of this diversity to the
basic properties of excitable mammalian cells.