Structural Information from Spin-Labelled Membrane-Bound Proteins

Abstract

Site-directed spin labelling (SDSL) in combination with electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for the investigation of the structure and conformational dynamics of biomolecules including membrane proteins under native-like conditions. EPR spectroscopy of the spin-labelled molecules provides information about the spin label side chain mobility, its solvent accessibility, the polarity of its immediate environment and intra- or intermolecular distances to another paramagnetic centre or spin label. This chapter provides an overview of the basics as well as recent progress in SDSL and related EPR techniques. Continuous wave EPR spectra analyses and pulse EPR techniques are reviewed with special emphasis on applications to the membrane-embedded sensory rhodopsin-transducer complex mediating the photophobic response of the halophilic archaeum Natronomonas pharaonis, the maltose ABC importer MalFGK(2) and the mechanosensitive channel MscS.