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We show that in the potassium channel KcsA, proton-dependent activation is followed by an inactivation process similar to C-type inactivation, and this process is suppressed by an E71A mutation in the pore helix. EPR spectroscopy demonstrates that the inner gate opens maximally at low pH regardless of the magnitude of the single-channel-open probability,(More)
Interconversion between conductive and non-conductive forms of the K(+) channel selectivity filter underlies a variety of gating events, from flicker transitions (at the microsecond timescale) to C-type inactivation (millisecond to second timescale). Here we report the crystal structure of the Streptomyces lividans K(+) channel KcsA in its open-inactivated(More)
In mechanosensitive (MS) channels, gating is initiated by changes in intra-bilayer pressure profiles originating from bilayer deformation. Here we evaluated two physical mechanisms as triggers of MS channel gating: the energetic cost of protein-bilayer hydrophobic mismatches and the geometric consequences of bilayer intrinsic curvature. Structural changes(More)
abstract The molecular architecture of the NH 2 and COOH termini of the prokaryotic potassium channel KcsA has been determined using site-directed spin-labeling methods and paramagnetic resonance EPR spectros-copy. Cysteine mutants were generated (residues 5–24 and 121–160) and spin labeled, and the X-band CW EPR spectra were obtained from(More)
Mechanosensitive channels act as membrane-embedded mechano-electrical switches, opening a large water-filled pore in response to lipid bilayer deformations. This process is critical to the response of living organisms to direct physical stimulation, such as in touch, hearing and osmoregulation. Here, we have determined the structural rearrangements that(More)
The coupled interplay between activation and inactivation gating is a functional hallmark of K(+) channels. This coupling has been experimentally demonstrated through ion interaction effects and cysteine accessibility, and is associated with a well defined boundary of energetically coupled residues. The structure of the K(+) channel KcsA in its fully open(More)
K+ channels undergo a time-dependent slow inactivation process that plays a key role in modulating cellular excitability. Here we show that in the prokaryotic proton-gated K+ channel KcsA, the number and strength of hydrogen bonds between residues in the selectivity filter and its adjacent pore helix determine the rate and extent of C-type inactivation.(More)
We have analyzed the local structure and dynamics of the prokaryotic voltage-dependent K+ channel (KvAP) at 0 millivolts, using site-directed spin labeling and electron paramagnetic resonance spectroscopy. We show that the S4 segment is located at the protein/lipid interface, with most of its charges protected from the lipid environment. Structurally, S4 is(More)
Modal-gating shifts represent an effective regulatory mechanism by which ion channels control the extent and time course of ionic fluxes. Under steady-state conditions, the K(+) channel KcsA shows three distinct gating modes, high-P(o), low-P(o) and a high-frequency flicker mode, each with about an order of magnitude difference in their mean open times.(More)
The mechanosensitive channel from Escherichia coli (Eco-MscL) responds to membrane lateral tension by opening a large, water-filled pore that serves as an osmotic safety valve. In an attempt to understand the structural dynamics of MscL in the closed state and under physiological conditions, we have performed a systematic site-directed spin labeling study(More)