title: Toward structural dynamics: protein motions viewed by chemical shift modulations and direct detection of C'N multiple-quantum relaxation.
abstract: Multiple quantum relaxation in proteins reveals unexpected relationships between correlated or anti-correlated conformational backbone dynamics in alpha-helices or beta-sheets. The contributions of conformational exchange to the relaxation rates of C'N coherences (i.e., double- and zero-quantum coherences involving backbone carbonyl (13)C' and neighboring amide (15)N nuclei) depend on the kinetics of slow exchange processes, as well as on the populations of the conformations and chemical shift differences of (13)C' and (15)N nuclei. The relaxation rates of C'N coherences, which reflect concerted fluctuations due to slow chemical shift modulations (CSMs), were determined by direct (13)C detection in diamagnetic and paramagnetic proteins. In well-folded proteins such as lanthanide-substituted calbindin (CaLnCb), copper,zinc superoxide dismutase (Cu,Zn SOD), and matrix metalloproteinase (MMP12), slow conformational exchange occurs along the entire backbone. Our observations demonstrate that relaxation rates of C'N coherences arising from slow backbone dynamics have positive signs (characteristic of correlated fluctuations) in beta-sheets and negative signs (characteristic of anti-correlated fluctuations) in alpha-helices. This extends the prospects of structure-dynamics relationships to slow time scales that are relevant for protein function and enzymatic activity.
authors.affiliation: Magnetic Resonance Center (CERM) and Department of Chemistry, University of Florence, Via L. Sacconi 3, 50019 Sesto Fiorentino, Italy.
authors.forename: Mirko
authors.initials: M
authors.lastname: Mori
authors.forename: Fatiha
authors.initials: F
authors.lastname: Kateb
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Bodenhausen
authors.forename: Mario
authors.initials: M
authors.lastname: Piccioli
authors.forename: Daniel
authors.initials: D
authors.lastname: Abergel
mesh_terms: D064026:Calbindins; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D002247:Carbon Isotopes; D002563:Cerium / Q000737:chemistry; D007811:Lanthanum / Q000737:chemistry; D053508:Matrix Metalloproteinase 12 / Q000737:chemistry* / Q000378:metabolism; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D017433:Protein Structure, Secondary; D011789:Quantum Theory; D064030:S100 Calcium Binding Protein G / Q000737:chemistry* / Q000378:metabolism; D013329:Structure-Activity Relationship; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000378:metabolism
chemical_list: D064026:Calbindins; D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D064030:S100 Calcium Binding Protein G; D002563:Cerium; D007811:Lanthanum; D013482:Superoxide Dismutase; D053508:Matrix Metalloproteinase 12; D002118:Calcium