title: Protein backbone motions viewed by intraresidue and sequential HN-Halpha residual dipolar couplings.
abstract: Triple resonance E.COSY-based techniques were used to measure intra-residue and sequential H(N)-H(alpha) residual dipolar couplings (RDCs) for the third IgG-binding domain of protein G (GB3), aligned in Pf1 medium. Measurements closely correlate with values predicted on the basis of an NMR structure, previously determined on the basis of a large number of one-bond backbone RDCs measured in five alignment media. However, in particular the sequential H(N)-H(alpha) RDCs are smaller than predicted for a static structure, suggesting a degree of motion for these internuclear vectors that exceeds that of the backbone amide N-H vectors. Of all experimentally determined GB3 structures available, the best correlation between experimental (1)H-(1)H couplings is observed for a GB3 ensemble, previously derived to generate a realistic picture of the conformational space sampled by GB3 (Clore and Schwieters, J Mol Biol 355:879-886, 2006). However, for both NMR and X-ray-derived structures the (1)H-(1)H couplings are found to be systematically smaller than expected on the basis of alignment tensors derived from (15)N-(1)H amide RDCs, assuming librationally corrected N-H bond lengths of 1.041 A.
authors.affiliation: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Beat
authors.initials: B
authors.lastname: Vögeli
authors.forename: Lishan
authors.initials: L
authors.lastname: Yao
authors.forename: Ad
authors.initials: A
authors.lastname: Bax
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D009038:Motion; D009584:Nitrogen / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011506:Proteins / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; C034284:IgG Fc-binding protein, Streptococcus; D011506:Proteins; D002244:Carbon; D006859:Hydrogen; D009584:Nitrogen