A carboxy-terminal inter-helix linker as the site of phosphatidylinositol 4,5-bisphosphate action on Kv7 (M-type) K+ channels.
The regulation of M-type (KCNQ [Kv7]) K(+) channels by phosphatidylinositol 4,5-bisphosphate (PIP(2)) has perhaps the best correspondence to physiological signaling, but the site of action and structural motif of PIP(2) on these channels have not been established. Using single-channel recordings of chimeras of Kv7.3 and 7.4 channels with highly differential PIP(2) sensitivities, we localized a carboxy-terminal inter-helix linker as the primary site of PIP(2) action. Point mutants within this linker in Kv7.2 and Kv7.3 identified a conserved cluster of basic residues that interact with the lipid using electrostatic and hydrogen bonds. Homology modeling of this putative PIP(2)-binding linker in Kv7.2 and Kv7.3 using the solved structure of Kir2.1 and Kir3.1 channels as templates predicts a structure of Kv7.2 and 7.3 very similar to the Kir channels, and to the seven-beta-sheet barrel motif common to other PIP(2)-binding domains. Phosphoinositide-docking simulations predict affinities and interaction energies in accord with the experimental data, and furthermore indicate that the precise identity of residues in the interacting pocket alter channel-PIP(2) interactions not only by altering electrostatic energies, but also by allosterically shifting the structure of the lipid-binding surface. The results are likely to shed light on the general structural mechanisms of phosphoinositide regulation of ion channels.
Hernandez
Ciria C
CC
Department of Physiology, MS 7756, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
Zaika
Oleg
O
Shapiro
Mark S
MS
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D051657:KCNQ1 Potassium Channel / Q000187:drug effects / Q000502:physiology*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000494:pharmacology*; D011485:Protein Binding
D051657:KCNQ1 Potassium Channel; D019269:Phosphatidylinositol 4,5-Diphosphate