Evolution and Structural Characteristics of Plant Voltage-Gated K+ Channels

Plant voltage-gated K+ channels have been referred to as plant Shakers in reference to animal Shaker channels, the first K+ channels identified. Recent advances in our knowledge of K+ channel evolution and structure have significantly deepened the divide between these plant and animal K+ channels, suggesting that it is time to completely retire the plant Shaker designation. Evolutionary genomics reveals that plant voltage-gated K+ channels and metazoan Shakers derive from distinct prokaryotic ancestors. The plant channels belong to a lineage that includes cyclic nucleotide-gated channels and metazoan ether-a-go-go and hyperpolarization-activated, cyclic nucleotide-gated channels. We refer to this lineage as the CNBD channel superfamily, because all these channels share a cytoplasmic gating domain homologous to cyclic nucleotide binding domains. The first structures of CNBD superfamily channels reveal marked differences in coupling between the voltage sensor and ion-conducting pore relative to metazoan Shaker channels. Viewing plant voltage-gated K+ channel function through the lens of CNBD superfamily structures should lead to insights into how these channels are regulated.