The impact of window functions on NMR-based paramagnetic relaxation enhancement measurements in membrane proteins.
Though challenging, solution NMR spectroscopy allows fundamental interrogation of the structure and dynamics of membrane proteins. One major technical hurdle in studies of helical membrane proteins by NMR is the difficulty of obtaining sufficient long range NOEs to determine tertiary structure. For this reason, long range distance information is sometimes sought through measurement of paramagnetic relaxation enhancements (PRE) of NMR nuclei as a function of distance from an introduced paramagnetic probe. Current PRE interpretation is based on the assumption of Lorentzian resonance lineshapes. However, in order to optimize spectral resolution, modern multidimensional NMR spectra are almost always subjected to resolution-enhancement, leading to distortions in the Lorentizian peak shape. Here it is shown that when PREs are derived using peak intensities (i.e., peak height) and linewidths from both real and simulated spectra that were produced using a wide range of apodization/window functions, that there is little variation in the distances determined (<1 A at the extremes). This indicates that the high degree of resolution enhancement required to obtain well-resolved spectra from helical membrane proteins is compatible with the use of PRE data as a source of distance restraints. While these conclusions are particularly important for helical membrane proteins, they are generally applicable to all PRE measurements made using resolution-enhanced data.
Van Horn
Wade D
WD
Department of Biochemistry and Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-8725, USA.
Beel
Andrew J
AJ
Kang
Congbao
C
Sanders
Charles R
CR
D000071443:12E7 Antigen; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry* / Q000235:genetics; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry* / Q000235:genetics; D017433:Protein Structure, Secondary / Q000502:physiology
D000071443:12E7 Antigen; D015703:Antigens, CD; C061828:CD99 protein, human; D015815:Cell Adhesion Molecules; C489622:KCNE1 protein, human; D024642:Potassium Channels, Voltage-Gated