Probing structural topology and dynamics of human KCNE3 membrane protein in lipid bilayers using site-directed spin labeling and electron paramagnetic resonance spectroscopy.

Abstract

KCNE3 is a single pass membrane spanning protein that modulates the function of the voltage gated potassium ion channel KCNQ1. Genetic mutations in the KCNE3 protein can result in multiple diseases such as long QT syndrome, atrial fibrillation, Mènière's disease, etc. Despite the biological significance, its structural and dynamic properties in a lipid bilayer are not yet fully understood. In this study, the structural topology and dynamic properties of KCNE3 were explored in lipid bilayers utilizing site-directed spin labeling (SDSL) and electron paramagnetic resonance (EPR) spectroscopy. Continuous wave EPR data indicated that the nitroxide spin labeled sidechains of KCNE3 in the transmembrane domain (TMD) are less mobile when compared to that of N and C-termini. Multiple nitroxide spin labeled amino acid sites have been studied using power saturation EPR to determine the membrane depth parameter (φ) of KCNE3 with respect to the POPC/POPG lipid bilayers. These results will be helpful for developing the topology model of KCNE3 in lipid bilayers.