Purification and Structural Characterization of the Epithelial Sodium Channel




Schmidt, Sean Larson

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The formation and regulation of transport channels within mammalian cells are directly related to their proper function. The epithelial sodium channel (ENaC) is responsible for regulating sodium reabsorbtion within the distal tubule of the nephron of the kidney. Gain-in-function mutations in ENaC cause prolongation of the time the channel remains in the plasma membrane resulting in hypertension. Understanding function of this channel and its abnormal behavior that causes disease requires knowledge of the channel complex structure. Previous studies have demonstrated that there are 3 distinct, but homologous subunits: a, P, and y. However, there is contradicting evidence on the subunit composition of this channel with two differing proposals of a 4-subunit and 9-subunit channel complex. We examined the subunit composition of ENaC using several traditional biochemistry techniques including crosslinking, affinity chromatography, cation and anion exchange chromatography, and polyacrylamide and agarose electrophoresis. For crosslinking, we covalently linked amino functional groups of lysine residues that are in close proximity. Native and denaturing polyacrylamide gel electrophoresis gels were used to determine if the subunits were crosslinked, and agarose gels to visualize the crosslinked complexes. The results were not consistent with predictions of a 4-subunit model. By examining the structure of ENaC, we will be aiding future research in the possible manipulation of the channel to treat or prevent diseases.



sodium channels, purification


Schmidt, S. L. (2006). Purification and structural characterization of the epithelial sodium channel (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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