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Fourier transform infrared spectroscopy reveals a rigid alpha-helical assembly for the tetrameric Streptomyces
J le Coutre1, H R Kaback, C K Patel
1Howard Hughes Medical Institute, Departments of Physiology and Microbiology and Molecular Genetics, Molecular Biology Institute, University of California, Los Angeles, CA 90095-1662, USA. lecoutre@hhmi.ucla.edu
Abstract:
The structure of the tetrameric K+ channel from Streptomyces lividans in a lipid bilayer environment was studied by polarized attenuated total reflection Fourier transform infrared spectroscopy. The channel displays approximately 43% alpha-helical and 25% beta-sheet content. In addition, H/D exchange experiments show that only 43% of the backbone amide protons are exchangeable with solvent. On average, the alpha-helices are tilted 33 degrees normal to the membrane surface. The results are discussed in relationship to the lactose permease of Escherichia coli, a membrane transport protein.