Moving gating charges through the gating pore in a Kv channel voltage sensor.
Voltage sensor domains (VSDs) regulate ion channels and enzymes by transporting electrically charged residues across a hydrophobic VSD constriction called the gating pore or hydrophobic plug. How the gating pore controls the gating charge movement presently remains debated. Here, using saturation mutagenesis and detailed analysis of gating currents from gating pore mutations in the Shaker Kv channel, we identified statistically highly significant correlations between VSD function and physicochemical properties of gating pore residues. A necessary small residue at position S240 in S1 creates a "steric gap" that enables an intracellular access pathway for the transport of the S4 Arg residues. In addition, the stabilization of the depolarized VSD conformation, a hallmark for most Kv channels, requires large side chains at positions F290 in S2 and F244 in S1 acting as "molecular clamps," and a hydrophobic side chain at position I237 in S1 acting as a local intracellular hydrophobic barrier. Finally, both size and hydrophobicity of I287 are important to control the main VSD energy barrier underlying transitions between resting and active states. Taken together, our study emphasizes the contribution of several gating pore residues to catalyze the gating charge transfer. This work paves the way toward understanding physicochemical principles underlying conformational dynamics in voltage sensors.
Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637.
Jérôme J
JJ
Lacroix
Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637.
H Clark
HC
Hyde
Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637.
Fabiana V
FV
Campos
Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637 fbezanilla@uchicago.edu.
Francisco
F
Bezanilla
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000502:physiology; D000818:Animals; D018360:Crystallography, X-Ray; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D015640:Ion Channel Gating / Q000502:physiology*; D007700:Kinetics; D051662:Kv1.1 Potassium Channel / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D051663:Kv1.2 Potassium Channel / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D017433:Protein Structure, Secondary / Q000502:physiology; D014982:Xenopus laevis
C496946:KCNA1 protein, human; C496969:KCNA2 protein, human; D051663:Kv1.2 Potassium Channel; D051662:Kv1.1 Potassium Channel
energy landscape; global fit; kinetic model