Structure refinement of transmembrane domain of KCNE3 in proteoliposomes using EPR spectroscopy.

KCNE3 is an integral membrane protein that regulates the function of several voltage gated potassium ion channels. A recent solution NMR studies by Sanders lab suggested that the structure of KCNE3 contains a α-helical transmembrane domain with a moderate degree of curvature as an inherent property of the protein. However, detailed structural information of KCNE3 in a lipid bilayer is still not fully understood. In this study, we utilize advanced electron paramagnetic resonance (EPR) technique of double electron electron resonance (DEER) spectroscopy to investigate structural conformation of the transmembrane domain of KCNE3 in proteoliposomes. DEER is a rapidly growing structure biology technique to study structural conformational of membrane protein by measuring distances within the range of 20-80 Å between two spin labeled sites. The DEER distance measurements were obtained for several double spin-labeled sites on the transmembrane domain of KCNE3 in POPC/POPG lipid bilayers. The DEER distance data were used as distances restraints in Xplor-NIH program to refine the structural model of transmembrane domain of KCNE3. This study will provide a guidance to understand structural-functional relationship of transmembrane domain of KCNE3 in lipid bilayer environment.