Structural dynamics of the Streptomyces lividans K+ channel (SKC1): secondary structure characterization from FTIR spectroscopy.
Fourier transform infrared (FTIR) spectroscopy was used to probe the secondary structure, orientation, and the kinetics of amide hydrogen-deuterium exchange (HX) of the small K+ channel from Streptomyces lividans. Frequency component analysis of the amide I band showed that SKC1 is composed of 44-46% alpha-helix, 21-24% beta-sheet, 10-12% turns and 18-20% unordered structures. The order parameter S of the helical component of SKC1 was between 0.60 and 0.69. Close to 80% of SKC1 amide protons exchange within approximately 3 h of D2O exposure, suggesting that the channel is largely accessible to solvent exchange. These results are consistent with a model of SKC1 in which helices slightly tilted from the membrane normal line the water-filled vestibules that flank the K+ selectivity filter.
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Department of Molecular Physiology and Biological Physics, and Center for Structural Biology, University of Virginia Health Sciences Center, Charlottesville 22906-0011, USA.
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D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D006859:Hydrogen / Q000737:chemistry; D008969:Molecular Sequence Data; D015221:Potassium Channels / Q000737:chemistry* / Q000302:isolation & purification; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013302:Streptomyces / Q000737:chemistry* / Q000378:metabolism
D001426:Bacterial Proteins; D015221:Potassium Channels; C107790:prokaryotic potassium channel; D006859:Hydrogen