how the channel select the ion? Charge and dimension. yes.
So how about potssium channel?
Look at this figure again. http://www.hhmi.org/research/investigators/images/mackinnon_fig1_lg.gif
the second pannel of the right figure. The backbone partial negatively charged
carbonyl oxygen atoms actually interact with the postively charged potassium.
Also the partical negative charge from C-term of helices play crucial part.
this is also true for chloride channel, though the geometry of its selective
f
