The crystal structure of chicken Kir2.2 at 3.1 Å resolution reveals binding sites along the ion conduction pathway that provide a structural basis for understanding rectification.
The 3.1 Å crystal structure of the eukaryotic Kir2.2 channel provides a structural basis for understanding inward rectification and suggests approaches for developing specific inhibitory agents.
Inward-rectifier potassium (K+) channels conduct K+ ions most efficiently in one direction, into the cell. Kir2 channels control the resting membrane voltage in many electrically excitable cells, and heritable mutations cause periodic paralysis and cardiac arrhythmia. We present the crystal structure of Kir2.2 from chicken, which, excluding the unstructured amino and carboxyl termini, is 90% identical to human Kir2.2. Crystals containing rubidium (Rb+), strontium (Sr2+), and europium (Eu3+) reveal binding sites along the ion conduction pathway that are both conductive and inhibitory. The sites correlate with extensive electrophysiological data and provide a structural basis for understanding rectification. The channel's extracellular surface, with large structured turrets and an unusual selectivity filter entryway, might explain the relative insensitivity of eukaryotic inward rectifiers to toxins. These same surface features also suggest a possible approach to the development of inhibitory agents specific to each member of the inward-rectifier K+ channel family.
Tao et al. (2009) studied this question. Crystal structure analysis of Kir2.2 was evaluated on Crystal structure of Kir2.2 at 3.1 Å resolution. The crystal structure of chicken Kir2.2 at 3.1 Å resolution reveals binding sites along the ion conduction pathway that provide a structural basis for understanding rectification.