NMR resonance assignments and secondary structure of a mutant form of the human KCNE1 channel accessory protein that exhibits KCNE3-like function
KCNQ1 (Q1) is a voltage-gated potassium channel that is modulated by members of the KCNE family, the best-characterized being KCNE1 (E1) and KCNE3 (E3). The Q1/E1 complex generates a channel with delayed activation and increased conductance. This complex is expressed in cardiomyocytes where it provides the IKs current that is critical for the repolarization phase of the cardiac action potential. The Q1/E3 complex, on the other hand, is expressed in epithelial cells of the colon and stomach, where it serves as a constitutively active leak channel to help maintain water and ion homeostasis. Studies show the single transmembrane segments (TMS) present in both E1 and E3 are essential to their distinct functions. More specifically, residues FTL located near the middle of the E1 TMS are essential for the delayed activation of Q1, while the corresponding TVG sites in E3 are critical for constitutive activation of the channel. Swapping these three residues leads to the switching of the functional properties for both Q1/E1FTL→TVG and Q1/E3TVG→FTL complexes. This work details the backbone assignments and chemical shifts for the E1FTL→TVG mutant, as determined using a suite of 3D NMR experiments along with specific and inverse amino acid isotopic labeling. The completed assignments can be used, in conjunction with other NMR experiments, to generate a 3D structure of E1FTL→TVG. The results of TALOS-N analysis of the chemical shifts are reported here. The E1FTL→TVG structure will be compared to the already available E1 and E3 structures to determine the roles that their TMS triplet motifs play in each protein to dictate their distinct channel-modulatory functions.
KeywordsKCNQ1 Voltage-gated potassium channel KCNE1 KCNE3 Backbone resonance assignments Membrane protein NMR
We thank Dr. Markus Voehler for help with setting up 3D NMR experiments and Dr. Keenan Taylor for assistance in processing NMR data.
This work was supported by NIH RO1 HL122010 and RO1 DC007416.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
These experiments comply with the current law of the country in which they were performed the USA.
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