Measurement of methyl 13C-1H cross-correlation in uniformly 13C-, 15N-, labeled proteins.
An understanding of side chain motions in protein is of great interest since side chains often play an important role in protein folding and intermolecular interactions. A novel method for measuring the dynamics of methyl groups in uniformly 13C-, 15N-labeled proteins has been developed by our group. The method relies on the difference in peak intensities of 13C quartet components of methyl groups, in a spectrum recording the free evolution of 13C under proton coupling in a constant-time period. Cross-correlated relaxation rates between 13C-1H dipoles can be easily measured from the intensities of the multiplet components. The degree of the methyl restrictions (S(' 2)) can be estimated from the cross-correlated relaxation rate. The method is demonstrated on a sample of human fatty acid binding protein in the absence of fatty acid. We obtained relaxation data for 33 out of 46 residues having methyl groups in apo-IFABP. It has been found that the magnitude of the CSA tensor of spin 13C in a methyl group could be estimated from the intensities of the 13C multiplet components.
D002247:Carbon Isotopes; D002352:Carrier Proteins / Q000737:chemistry; D050556:Fatty Acid-Binding Proteins; D006801:Humans; D006859:Hydrogen; D008280:Magnetics; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry*; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011506:Proteins / Q000737:chemistry*
D002247:Carbon Isotopes; D002352:Carrier Proteins; D050556:Fatty Acid-Binding Proteins; D009587:Nitrogen Isotopes; D011506:Proteins; C051224:methyl radical; D006859:Hydrogen; D008697:Methane