6v1x | pdb_00006v1x
Cryo-EM Structure of the Hyperpolarization-Activated Potassium Channel KAT1: Tetramer
Structural highlights
Function[KAT1_ARATH] Highly selective inward-rectifying potassium channel. This voltage-gated channel could mediate long-term potassium influx into guard cells leading to stomatal opening. Assuming opened or closed conformations in response to the voltage difference across the membrane, the channel is activated by hyperpolarization. The channel activity is enhanced upon external acidification. Also permeable to ammonium ions. Blocked by tetraethylammonium and barium ions.[1] Publication Abstract from PubMedVoltage-gated potassium (Kv) channels coordinate electrical signalling and control cell volume by gating in response to membrane depolarization or hyperpolarization. However, although voltage-sensing domains transduce transmembrane electric field changes by a common mechanism involving the outward or inward translocation of gating charges(1-3), the general determinants of channel gating polarity remain poorly understood(4). Here we suggest a molecular mechanism for electromechanical coupling and gating polarity in non-domain-swapped Kv channels on the basis of the cryo-electron microscopy structure of KAT1, the hyperpolarization-activated Kv channel from Arabidopsis thaliana. KAT1 displays a depolarized voltage sensor, which interacts with a closed pore domain directly via two interfaces and indirectly via an intercalated phospholipid. Functional evaluation of KAT1 structure-guided mutants at the sensor-pore interfaces suggests a mechanism in which direct interaction between the sensor and the C-linker hairpin in the adjacent pore subunit is the primary determinant of gating polarity. We suggest that an inward motion of the S4 sensor helix of approximately 5-7 A can underlie a direct-coupling mechanism, driving a conformational reorientation of the C-linker and ultimately opening the activation gate formed by the S6 intracellular bundle. This direct-coupling mechanism contrasts with allosteric mechanisms proposed for hyperpolarization-activated cyclic nucleotide-gated channels(5), and may represent an unexpected link between depolarization- and hyperpolarization-activated channels. Electromechanical coupling in the hyperpolarization-activated K(+) channel KAT1.,Clark MD, Contreras GF, Shen R, Perozo E Nature. 2020 Jul;583(7814):145-149. doi: 10.1038/s41586-020-2335-4. Epub 2020 May, 27. PMID:32461693[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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