title: NMR solution structure and dynamics of motilin in isotropic phospholipid bicellar solution.
abstract: The structure and dynamics of the gastrointestinal peptide hormone motilin, consisting of 22 amino acid residues, have been studied in the presence of isotropic q = 0.5 phospholipid bicelles. The NMR solution structure of the peptide in acidic bicelle solution was determined from 203 NOE-derived distance constraints and six backbone torsion angle constraints. Dynamic properties for the 13Calpha-1H vector in Leu10 were determined for motilin specifically labeled with 13C at this position by analysis of multiple-field relaxation data. The structure reveals an ordered alpha-helical conformation between Glu9 and Lys20. The N-terminus is also well structured with a turn resembling that of a classical beta-turn. The 13C dynamics clearly show that motilin tumbles slowly in solution, with a correlation time characteristic of a large object. It was also found that motilin has a large degree of local flexibility as compared with what has previously been reported in SDS micelles. The results show that motilin interacts with the bicelle, displaying motional properties of a peptide bound to a membrane. In comparison, motilin in neutral bicelles seems less structured and more flexible. This study shows that the small isotropic bicelles are well suited for use as membrane-mimetic for structural as well as dynamical investigations of membrane-bound peptides by high-resolution NMR.
authors.affiliation: Department of Biochemistry and Biophysics, Arrhenius Laboratory, Stockholm University, 10691 Stockholm, Sweden.
authors.forename: August
authors.initials: A
authors.lastname: Andersson
authors.forename: Lena
authors.initials: L
authors.lastname: Mäler
mesh_terms: D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D008051:Lipid Bilayers / Q000737:chemistry; D008823:Micelles; D008958:Models, Molecular; D009037:Motilin / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D010455:Peptides / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry*; D011487:Protein Conformation; D012996:Solutions; D013816:Thermodynamics
chemical_list: D008051:Lipid Bilayers; D008823:Micelles; D010455:Peptides; D010743:Phospholipids; D012996:Solutions; D009037:Motilin