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Title: A structure-function study of the TWIK-1 K2P channel
Author: Wahab, Mohd Firdaus Abd
ISNI:       0000 0004 6497 9983
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2015
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Two-pore domain potassium (K2P) channels play a role in regulating the resting mem- brane potential of cells and therefore play a major role in the function of both excitable and non-excitable cells. One of the K2P family members is the Tandem-pore Weak Inwardly-rectifying Potassium (TWIK-1) channel. It is mostly found in the kidney and heart. However, not much is known about the biophysical properties and regulation of this channel. In the first part of this study, the presence of a hydrophobic cuff at the inner pore side of the channel is identified and characterised. This cuff acts as a barrier to water permeation, and by extension, ion flow through the channel. Using molecular dynamic simulations and electrophysiology, two leucine residues, L146 and L261, were identified as the primary constituents of this hydrophobic cuff. Systematic mutagenesis of these residues reveals that the barrier against pore hydration can be overcome by introducing polar side chains into these positions. This study also addresses the problem of TWIK-1 functional expression at the surface membrane. Suppression of TWIK-1 functional activity has been thought to be caused by binding of a small ubiquitin-like modifier (SUMO) to a lysine residue in the C-helix (K274). However, it has also been suggested that TWIK-1 at the surface membrane is rapidly internalised into endosomes via the endocytosis pathway. My results suggest that the latter explanation is more likely. The second major part of this study focused on the structure and function of the amphipathic helix near the c-terminus of the protein. This 'C-helix' lies parallel to the intracellular membrane surface. Using scanning mutagenesis and electrophysiological measurements, a trio of positively-charged residues (K274/R277/K278) that faces the inner pore were identified as playing an important role in the functional expression of TWIK-1 currents by influencing the electrostatic charges at the intracellular pore mouth of TWIK-1. Overall this thesis provides new insights into the structural features which control the functional activity of the TWIK-1 potassium channel.
Supervisor: Tucker, Stephen J. Sponsor: Malaysian Government
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available