title: Proton-detected 2D radio frequency driven recoupling solid-state NMR studies on micelle-associated cytochrome-b(5).
abstract: Solid-state NMR spectroscopy is increasingly used in the high-resolution structural studies of membrane-associated proteins and peptides. Most such studies necessitate isotopically labeled ((13)C, (15)N and (2)H) proteins/peptides, which is a limiting factor for some of the exciting membrane-bound proteins and aggregating peptides. In this study, we report the use of a proton-based slow magic angle spinning (MAS) solid-state NMR experiment that exploits the unaveraged (1)H-(1)H dipolar couplings from a membrane-bound protein. We have shown that the difference in the buildup rates of cross-peak intensities against the mixing time - obtained from 2D (1)H-(1)H radio frequency-driven recoupling (RFDR) and nuclear Overhauser effect spectroscopy (NOESY) experiments on a 16.7-kDa micelle-associated full-length rabbit cytochrome-b5 (cytb5) - can provide insights into protein dynamics and could be useful to measure (1)H-(1)H dipolar couplings. The experimental buildup curves compare well with theoretical simulations and are used to extract relaxation parameters. Our results show that due to fast exchange of amide protons with water in the soluble heme-containing domain of cyb5, coherent (1)H-(1)H dipolar interactions are averaged out for these protons while alpha and side chain protons show residual dipolar couplings that can be obtained from (1)H-(1)H RFDR experiments. The appearance of resonances with distinct chemical shift values in (1)H-(1)H RFDR spectra enabled the identification of residues (mostly from the transmembrane region) of cytb5 that interact with micelles.
authors.affiliation: Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States.
authors.forename: Manoj Kumar
authors.initials: MK
authors.lastname: Pandey
authors.affiliation: Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States.
authors.forename: Subramanian
authors.initials: S
authors.lastname: Vivekanandan
authors.affiliation: Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States.
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Yamamoto
authors.affiliation: Department of Anesthesiology, University of Michigan, VA Medical Center, Ann Arbor, MI 48105, United States.
authors.forename: Sangchoul
authors.initials: S
authors.lastname: Im
authors.affiliation: Department of Anesthesiology, University of Michigan, VA Medical Center, Ann Arbor, MI 48105, United States.
authors.forename: Lucy
authors.initials: L
authors.lastname: Waskell
authors.affiliation: Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States. Electronic address: ramamoor@umich.edu.
authors.forename: Ayyalusamy
authors.initials: A
authors.lastname: Ramamoorthy
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015786:Cytochromes b5 / Q000737:chemistry* / Q000648:ultrastructure*; D008823:Micelles; D008969:Molecular Sequence Data; D011487:Protein Conformation; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D011817:Rabbits; D012815:Signal Processing, Computer-Assisted
chemical_list: D008823:Micelles; D015786:Cytochromes b5
keywords: Cytochrome-b(5); Membrane protein; NOESY; RFDR