DEER EPR measurements for membrane protein structures via bifunctional spin labels and lipodisq nanoparticles.

Sahu ID, McCarrick RM, Troxel KR, Zhang R, Smith HJ, Dunagan MM, Swartz MS, Rajan PV, Kroncke BM, Sanders CR, Lorigan GA
Biochemistry. 2013 52 (38): 6627-32

PMID: 23984855 · PMCID: PMC3826088 · DOI:10.1021/bi4009984

Pulsed EPR DEER structural studies of membrane proteins in a lipid bilayer have often been hindered by difficulties in extracting accurate distances when compared to those of globular proteins. In this study, we employed a combination of three recently developed methodologies, (1) bifunctional spin labels (BSL), (2) SMA-Lipodisq nanoparticles, and (3) Q band pulsed EPR measurements, to obtain improved signal sensitivity, increased transverse relaxation time, and more accurate and precise distances in DEER measurements on the integral membrane protein KCNE1. The KCNE1 EPR data indicated an ∼2-fold increase in the transverse relaxation time for the SMA-Lipodisq nanoparticles when compared to those of proteoliposomes and narrower distance distributions for the BSL when compared to those of the standard MTSL. The certainty of information content in DEER data obtained for KCNE1 in SMA-Lipodisq nanoparticles is comparable to that in micelles. The combination of techniques will enable researchers to potentially obtain more precise distances in cases where the traditional spin labels and membrane systems yield imprecise distance distributions.

MeSH Terms (8)

Cyclic N-Oxides Electron Spin Resonance Spectroscopy Lipid Bilayers Membrane Proteins Mesylates Nanoparticles Potassium Channels, Voltage-Gated Spin Labels

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