Comparative study of the structure and interaction of the pore helices of the hERG and Kv1.5 potassium channels in model membranes
- 234 Downloads
The hERG channel is a voltage-gated potassium channel found in cardiomyocytes that contributes to the repolarization of the cell membrane following the cardiac action potential, an important step in the regulation of the cardiac cycle. The lipids surrounding K+ channels have been shown to play a key role in their regulation, with anionic lipids shown to alter gating properties. In this study, we investigate how anionic lipids interact with the pore helix of hERG and compare the results with those from Kv1.5, which possesses a pore helix more typical of K+ channels. Circular dichroism studies of the pore helix secondary structure reveal that the presence of the anionic lipid DMPS within the bilayer results in a slight unfolding of the pore helices from both hERG and Kv1.5, albeit to a lesser extent for Kv1.5. In the presence of anionic lipids, the two pore helices exhibit significantly different interactions with the lipid bilayer. We demonstrate that the pore helix from hERG causes significant perturbation to the order in lipid bicelles, which contrasts with only small changes observed for Kv1.5. These observations suggest that the atypical sequence of the pore helix of hERG may play a key role in determining how anionic lipids influence its gating.
KeywordsIon channel Bicelles Lipids Dodecylphosphocholine Nuclear magnetic resonance Circular dichroism
This work was supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada. MB wishes to thank the Université du Québec à Montréal, the NSERC Training Program in Bionanomachines, the Canadian Institutes of Health Research Strategic Training Initiative in Chemical Biology, and the Centre Québécois sur les Matériaux Fonctionnels (CQMF) for the award of scholarships. Phuong Trang Nguyen is gratefully acknowledged for the peptide synthesis and purification. IM is a member of the CQMF and the Groupe de Recherche Axé sur la Structure des Protéines (GRASP). SB is a member of the GRASP and the Quebec Network for Research on Protein Function, Structure, and Engineering, PROTEO.
- Briggs ELA, Gomes RGB, Elhussein M, Collier W, Findlow IS, Khalid S, McCormick CJ, Williamson PTF (2015) Interaction between the NS4B amphipathic helix, AH2, and charged lipid headgroups alters membrane morphology and AH2 oligomeric state—Implications for the Hepatitis C virus life cycle. Bba-Biomembranes 1848:1671–1677CrossRefGoogle Scholar
- Damberg P, Jarvet J, Gräslund A (2001) Micellar systems as solvents in peptide and protein structure determination. In: Thomas L, James VD, Uli S (eds) Methods in enzymology, vol 339. Academic Press, New York, pp 271–285. doi: 10.1016/S0076-6879(01)39318-7
- Hite RK, Butterwick JA, MacKinnon R (2014) Phosphatidic acid modulation of Kv channel voltage sensor function. eLife 3Google Scholar
- Rance M, Byrd RA (1983) Obtaining high-fidelity spin-1/2 powder spectra in anisotropic media—phase-cycled Hahn echo spectroscopy. J Magn Reson 52:221–240Google Scholar
- van der Cruijsen EAW, Nand D, Weingarth M, Prokofyev A, Hornig S, Cukkemane AA, Bonvin AMJJ, Becker S, Hulse RE, Perozo E, Pongs O, Baldus M (2013) Importance of lipid–pore loop interface for potassium channel structure and function. Proc Nat Acad Sci USA 110:13008–13013CrossRefPubMedPubMedCentralGoogle Scholar