title: Membrane interactions in small fast-tumbling bicelles as studied by 31P NMR.
abstract: Small fast-tumbling bicelles are ideal for studies of membrane interactions at molecular level; they allow analysis of lipid properties using solution-state NMR. In the present study we used 31P NMR relaxation to obtain detailed information on lipid head-group dynamics. We explored the effect of two topologically different membrane-interacting peptides on bicelles containing either dimyristoylphosphocholine (DMPC), or a mixture of DMPC and dimyristoylphosphoglycerol (DMPG), and dihexanoylphosphocholine (DHPC). KALP21 is a model transmembrane peptide, designed to span a DMPC bilayer and dynorphin B is a membrane surface active neuropeptide. KALP21 causes significant increase in bicelle size, as evidenced by both dynamic light scattering and 31P T2 relaxation measurements. The effect of dynorphin B on bicelle size is more modest, although significant effects on T2 relaxation are observed at higher temperatures. A comparison of 31P T1 values for the lipids with and without the peptides showed that dynorphin B has a greater effect on lipid head-group dynamics than KALP21, especially at elevated temperatures. From the field-dependence of T1 relaxation data, a correlation time describing the overall lipid motion was derived. Results indicate that the positively charged dynorphin B decreases the mobility of the lipid molecules--in particular for the negatively charged DMPG--while KALP21 has a more modest influence. Our results demonstrate that while a transmembrane peptide has severe effects on overall bilayer properties, the surface bound peptide has a more dramatic effect in reducing lipid head-group mobility. These observations may be of general importance for understanding peptide-membrane interactions.
authors.affiliation: Laboratory of Structural Chemistry and Biology, Institute of Chemistry, Eötvös Loránd University, H-1117 Budapest, Hungary. Electronic address: abodor@chem.elte.hu.
authors.forename: Andrea
authors.initials: A
authors.lastname: Bodor
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Debrecen, H-4032 Debrecen, Hungary.
authors.forename: Katalin E
authors.initials: KE
authors.lastname: Kövér
authors.affiliation: Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm Sweden. Electronic address: lena.maler@dbb.su.se.
authors.forename: Lena
authors.initials: L
authors.lastname: Mäler
mesh_terms: D000595:Amino Acid Sequence; D016880:Anisotropy; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism; D004399:Dynorphins / Q000737:chemistry / Q000378:metabolism; D004723:Endorphins / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D007834:Lasers; D008027:Light; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008563:Membrane Lipids / Q000737:chemistry* / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D009038:Motion; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D010715:Phosphatidylglycerols / Q000737:chemistry / Q000378:metabolism; D010742:Phospholipid Ethers / Q000737:chemistry / Q000378:metabolism; D010759:Phosphorus Isotopes; D011485:Protein Binding; D012542:Scattering, Radiation
chemical_list: C052298:1,2-dihexadecyl-sn-glycero-3-phosphocholine; D004723:Endorphins; D008051:Lipid Bilayers; D008563:Membrane Lipids; D008565:Membrane Proteins; D010455:Peptides; D010715:Phosphatidylglycerols; D010742:Phospholipid Ethers; D010759:Phosphorus Isotopes; D004399:Dynorphins; C036200:rimorphin; C002773:dimyristoylphosphatidylglycerol; D004134:Dimyristoylphosphatidylcholine
keywords: Bicelle; Dynamic light scattering; Membrane protein; Relaxation study; Solution (31)P NMR spectroscopy