Sequence conservation among K1 channels
(including ones with two and six membrane-
spanning segments), as well as cyclic
nucleotide-gated cation channels, is strongest
for the amino acids corresponding to
the pore region and the inner helix. Even
Na1 and Ca21 channels show distant relatedness
over these segments. The teepee architecture
of the K1 channel pore likely
will be a general feature of all of these
cation channels, with four inner helices
arranged like the poles of a teepee, four pore
helices, and a selectivity filter—tuned to
select the appropriate cation—located close
to the extracellular surface.