title: How uniform is the peptide plane geometry? A high-accuracy NMR study of dipolar Cα-C'/H N-N cross-correlated relaxation.
abstract: Highly precise and accurate measurements of very small NMR cross-correlated relaxation rates, namely those between protein H (i) (N) -N(i) and C (i-1) (α) -C(i-1)' dipoles, are demonstrated with an error of 0.03 s(-1) for GB3. Because the projection angles between the two dipole vectors are very close to the magic angle the rates range only from -0.2 to +0.2 s(-1). Small changes of the average vector orientations have a dramatic impact on the relative values. The rates suggest deviation from idealized peptide plane geometry caused by twists around the C'-N bonds and/or pyramidalization of the nitrogen atoms. A clear alternating pattern along the sequence is observed in β strands 1, 3 and 4 of GB3, where the side chains of almost all residues with large positive rates are solvent exposed. In the α helix all rates are relatively large and positive. Some of the currently most accurate structures of GB3 determined by both high resolution X-ray crystallography and NMR are in satisfactory agreement with the experimental rates in the helix and β strand 3, but not in the loops and the two central strands of the sheet for which no alternating pattern is predicted.
authors.affiliation: Laboratory of Physical Chemistry, Swiss Federal Institute of Technology, ETH-Hönggerberg, 8093, Zürich, Switzerland. beat.voegeli@phys.chem.ethz.ch
authors.forename: Beat
authors.initials: B
authors.lastname: Vögeli
mesh_terms: D018360:Crystallography, X-Ray; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D015203:Reproducibility of Results
chemical_list: D011506:Proteins