Thermal and chemical unfolding and refolding of a eukaryotic sodium channel
Charalambous, Kalypso and O’Reilly, Andrias O. and Bullough, P.A. and Wallace, Bonnie A. (2009) Thermal and chemical unfolding and refolding of a eukaryotic sodium channel. Biochimica et Biophysica Acta (BBA) - Biomembranes 1788 (6), pp. 1279-1286. ISSN 0006-3002.
Voltage-gated sodium channels are dynamic membrane proteins essential for signaling in nervous and muscular systems. They undergo substantial conformational changes associated with the closed, open and inactivated states. However, little information is available regarding their conformational stability. In this study circular dichroism spectroscopy was used to investigate the changes in secondary structure accompanying chemical and thermal denaturation of detergent-solubilised sodium channels isolated from Electrophorus electricus electroplax. The proteins appear to be remarkably resistant to either type of treatment, with “denatured” channels, retaining significant helical secondary structure even at 77 °C or in 10% SDS. Further retention of helical secondary structure at high temperature was observed in the presence of the channel-blocking tetrodotoxin. It was possible to refold the thermally-denatured (but not chemically-denatured) channels in vitro. The correctly refolded channels were capable of undergoing the toxin-induced conformational change indicative of ligand binding. In addition, flux measurements in liposomes showed that the thermally-denatured (but not chemically-denatured) proteins were able to re-adopt native, active conformations. These studies suggest that whilst sodium channels must be sufficiently flexible to undergo major conformational changes during their functional cycle, the proteins are highly resistant to unfolding, a feature that is important for maintaining structural integrity during dynamic processes.
|Keyword(s) / Subject(s):||Voltage-gated sodium channel, Protein folding, Membrane protein, Secondary structure, Circular dichroism spectroscopy, Toxin binding|
|School:||Birkbeck Schools and Departments > School of Science > Biological Sciences|
|Research Centre:||Bioinformatics, Bloomsbury Centre for, Structural Molecular Biology, Institute of (ISMB)|
|Date Deposited:||04 Aug 2010 14:09|
|Last Modified:||07 Dec 2016 15:05|
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