Recently, Michael_Lebow at Brown.edu wrote [in part, please excuse the paraphrase]
> Why are there so many K+ channels?
drawing the reply from st004131 at brownvm.brown.edu
> Because there are so many K+ channel subunits.
Now, I have to agree with this, and I also have to agree with Lyle at ai.mit.edu t
hat there must be some functional basis for this (especially when one tries to
put this into an evolutionary framework). However, after reading some of the li
terature on receptor diversity (e.g., serotonin receptor subtypes), I'm not sur
e. Even using the idea of tuning, it's hard to imagine the utility of >10 subty
pes. And this pales in comparison to some of the ionophores, like the GABA-A re
ceptor: do the permutations on the known subunits, and one has about 2000 possi
ble receptors. I'm sure I'm glossing over a few fine points (say, subunit alpha
-1 is never coexpressed with beta-3 or -4, or something like that), but even if
we cut the number to 200, the question remains: what possible role could this
number of receptors have?
