Expression, purification, detergent screening and solution NMR backbone assignment of the human potassium channel accessory subunit MiRP1.

MiRP1 (MinK related protein 1) is a membrane protein in the KCNE family. It can associate with and modulate various voltage gated potassium channels. Mutations in human MiRP1 have been found to cause many congenital and acquired long QT syndromes, which are potentially life-threatening cardiac arrhythmias. Here, human MiRP1 was over-expressed in Escherichia coli, purified and eluted into different detergents. Two dimensional (1)H-(15)N correlated solution nuclear magnetic resonance (NMR) spectra of the human MiRP1 in four different detergent micelles indicated that high resolution solution NMR spectrum can be obtained for human MiRP1 in detergent lyso-myristoylphosphatidylglycerol (LMPG). Circular dichroism (CD) spectroscopy of human MiRP1 indicated a high content of alpha-helical secondary structure in LMPG. Backbone assignments of most MiRP1 residues were achieved through a series of triple resonance NMR experiments. Secondary structure analysis based on backbone chemical shifts showed several stretches of alpha-helices along the primary sequence of MiRP1 in LMPG.