Ion Channel Structure and the Promise of Bacteria : Cyclic Nucleotide-Gated Channels in the Queue

To date it has proved very difficult to express eukaryotic channels in Escherichia coli or otherwise obtain enough of these proteins for crystallization. So, unbeknownst to bacteria, they have been making a major contribution to ion channel research since 1998. So much so that everyone in the ion channel community eagerly anticipates the next promising bacterial channel and the big payoff that comes from the elucidation of its three-dimensional structure. This golden age of bacterial channels started when Rod MacKinnon and his colleagues crystallized and determined the structure of the KcsA K⁺ channel in 1998, giving us the first high-resolution picture of an ion-selective channel (Doyle et al., 1998; Morais-Cabral et al., 2001; Zhou et al., 2001). KcsA is a member of a superfamily of tetrameric cation channels that includes K⁺, Na⁺, and Ca²⁺ channels,...