A Multi-Faceted Study of the Voltage Sensor in Voltage-Gated Potassium Channels

• Author / Creator

  Sand, Rheanna M.

• Voltage-gated potassium (Kv) channels regulate the flow of potassium ions across the cell membrane of nerves and muscles. Proper functioning of these and other voltage-gated ion channels is critical for an animal to sense the environment and respond quickly to stimuli. Dysfunctional Kv channels, whether inherited or induced by pharmacological agents, can be the root cause of disease or death. Kv proteins have a voltage sensing domain that physically moves across the cell membrane during activation, but a complete picture of this process is lacking. The work presented in this thesis addressed the structure-function relationships within the voltage sensing domain of Kv channels using three distinct approaches. First, a previously unknown jellyfish Kv channel was sequenced in order to diversify the pool of known channels, which is heavily biased toward mammalian sequences. The voltage-dependent properties of this new channel were compared to those of known, mammalian channels to better understand the processes of voltage-dependent gating. Secondly, a well-studied mammalian channel was altered in a way that allowed for an estimation of the atomic distance between two helices in the voltage sensing domain. Molecular dynamics simulations were used to calculate Gibbs free energy difference between two states, which was compared to experimental data to triangulate the most likely actual distance between the S3 and S4 helices. Lastly, several experiments were undertaken to locate the pharmacological receptor site on Kv channels for 6-bromo-2-mercaptotryptamine or BrMT. This gastropod toxin is a modulator of Kv channels that interferes with the gating process. Attempts to locate that binding site through mutagenesis and electrophysiological assay were not conclusive. In summary, the atypical behavior of the novel jellyfish channel demonstrated the utility of isolating and characterizing Kv sequences from basally-branching organisms; the comparison of free energy from molecular dynamics with that of real-world data allowed us to estimate atomic distances in a Kv channel; and BrMT may represent a new mechanistic class of Kv channel blocker but more work is needed to determine the binding site.

• Subjects / Keywords

  • Potassium channels
  • Free energy
  • Pharmacology
  • Biophysics

• Graduation date

  Spring 2012

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3840Q

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.