title: Variation of molecular alignment as a means of resolving orientational ambiguities in protein structures from dipolar couplings.
abstract: Residual dipolar couplings for pairs of proximate magnetic nuclei in macromolecules can easily be measured using high-resolution NMR methods when the molecules are dissolved in dilute liquid crystalline media. The resulting couplings can in principle be used to constrain the relative orientation of molecular fragments in macromolecular systems to build a complete structure. However, determination of relative fragment orientations based on a single set of residual dipolar couplings is inherently hindered by the multi-valued nature of the angular dependence of the dipolar interaction. Even with unlimited dipolar data, this gives rise to a fourfold degeneracy in fragment orientations. In this Communication, we demonstrate a procedure based on an order tensor analysis that completely removes this degeneracy by combining residual dipolar coupling measurements from two alignment media. Application is demonstrated on (15)N-(1)H residual dipolar coupling data acquired on the protein zinc rubredoxin from Clostridium pasteurianum dissolved in two different bicelle media.
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: H M
authors.initials: HM
authors.lastname: Al-Hashimi
authors.forename: H
authors.initials: H
authors.lastname: Valafar
authors.forename: M
authors.initials: M
authors.lastname: Terrell
authors.forename: E R
authors.initials: ER
authors.lastname: Zartler
authors.forename: M K
authors.initials: MK
authors.lastname: Eidsness
authors.forename: J H
authors.initials: JH
authors.lastname: Prestegard
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D003013:Clostridium / Q000737:chemistry / Q000145:classification; D003460:Crystallization; D006859:Hydrogen; D006860:Hydrogen Bonding; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009587:Nitrogen Isotopes; D011487:Protein Conformation; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry*; D012416:Rubredoxins / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D046911:Macromolecular Substances; D009587:Nitrogen Isotopes; D011506:Proteins; D012416:Rubredoxins; C077196:rubredoxin protein, Clostridium pasteurianum; D006859:Hydrogen