title: Positioning of micelle-bound peptides by paramagnetic relaxation enhancements.
abstract: Many peptides, proteins, and drugs interact with biological membranes, and knowing the mode of binding is essential to understanding their biological functions. To obtain the complete orientation and immersion depth of such a compound, the membrane-mimetic system (micelle) is placed in an aqueous buffer containing the soluble and inert paramagnetic contrast agent Gd(DTPA-BMA). Paramagnetic relaxation enhancements (PREs) of a specific nucleus then depend only on its distance from the surface. The positioning of a structurally characterized compound can be obtained by least-squares fitting of experimental PREs to the micelle center position. This liquid-state NMR approach, which does not rely on isotopic labeling or chemical modification, has been applied to determine the location of the presumed transmembrane region 7 of yeast V-ATPase (TM7) and the membrane-bound antimicrobial peptide CM15 in micelles. TM7 binds in a trans-micelle orientation with the N-terminus being slightly closer to the surface than the C-terminus. CM15 is immersed unexpectedly deep into the micelle with the more hydrophilic side of the helix being closer to the surface than the hydrophobic one.
authors.affiliation: Institute of Chemistry/Organic and Bioorganic Chemistry, University of Graz, Austria. klaus.zangger@uni-graz.at
authors.forename: Klaus
authors.initials: K
authors.lastname: Zangger
authors.forename: Michal
authors.initials: M
authors.lastname: Respondek
authors.forename: Christoph
authors.initials: C
authors.lastname: Göbl
authors.forename: Walter
authors.initials: W
authors.lastname: Hohlweg
authors.forename: Kenneth
authors.initials: K
authors.lastname: Rasmussen
authors.forename: Günter
authors.initials: G
authors.lastname: Grampp
authors.forename: Tobias
authors.initials: T
authors.lastname: Madl
mesh_terms: D008823:Micelles; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry*; D017434:Protein Structure, Tertiary
chemical_list: D008823:Micelles; D010455:Peptides