ABSTRACT
Most ion channels can be dened as a multisubunit complex with the ion conduction pathway formed at the common interface, generally the center of the molecule (Doyle 2004). is applies to potassium channels, sodium channels, calcium channels, cationic channels, and anion channels and still holds true whether they are voltage-dependent, ligand-gated, or mechanically gated channels. e two groups that do not fall into this classication are the proton channels and some chloride channels such as the Cl-(chloride) channels (CLC). is may be due to the special movement mechanism of protons in solution and the fact that CLC channels evolved from Cl−/H+ antiporters, respectively (Miller 2006; Ramsey et al. 2006; Sasaki et al. 2006; Lim et al. 2012). e main point is that all of the channels are multisubunit complexes, and therefore, there this additional complexity needs to be incorporated into the process of structure determination.
