title: Structure of a double transmembrane fragment of a G-protein-coupled receptor in micelles.
abstract: The structure and dynamic properties of an 80-residue fragment of Ste2p, the G-protein-coupled receptor for alpha-factor of Saccharomyces cerevisiae, was studied in LPPG micelles with the use of solution NMR spectroscopy. The fragment Ste2p(G31-T110) (TM1-TM2) consisted of 19 residues from the N-terminal domain, the first TM helix (TM1), the first cytoplasmic loop, the second TM helix (TM2), and seven residues from the first extracellular loop. Multidimensional NMR experiments on [(15)N], [(15)N, (13)C], [(15)N, (13)C, (2)H]-labeled TM1-TM2 and on protein fragments selectively labeled at specific amino acid residues or protonated at selected methyl groups resulted in >95% assignment of backbone and side-chain nuclei. The NMR investigation revealed the secondary structure of specific residues of TM1-TM2. TALOS constraints and NOE connectivities were used to calculate a structure for TM1-TM2 that was highlighted by the presence of three alpha-helices encompassing residues 39-47, 49-72, and 80-103, with higher flexibility around the internal Arg(58) site of TM1. RMSD values of individually superimposed helical segments 39-47, 49-72, and 80-103 were 0.25 +/- 0.10 A, 0.40 +/- 0.13 A, and 0.57 +/- 0.19 A, respectively. Several long-range interhelical connectivities supported the folding of TM1-TM2 into a tertiary structure typified by a crossed helix that splays apart toward the extracellular regions and contains considerable flexibility in the G(56)VRSG(60) region. (15)N-relaxation and hydrogen-deuterium exchange data support a stable fold for the TM parts of TM1-TM2, whereas the solvent-exposed segments are more flexible. The NMR structure is consistent with the results of biochemical experiments that identified the ligand-binding site within this region of the receptor.
authors.affiliation: Institute of Organic Chemistry, University of Zurich, Zurich, Switzerland.
authors.forename: Alexey
authors.initials: A
authors.lastname: Neumoin
authors.forename: Leah S
authors.initials: LS
authors.lastname: Cohen
authors.forename: Boris
authors.initials: B
authors.lastname: Arshava
authors.forename: Subramanyam
authors.initials: S
authors.lastname: Tantry
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Becker
authors.forename: Oliver
authors.initials: O
authors.lastname: Zerbe
authors.forename: Fred
authors.initials: F
authors.lastname: Naider
mesh_terms: D000595:Amino Acid Sequence; D005989:Glycerides; D008024:Ligands; D008823:Micelles; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D051964:Receptors, Mating Factor / Q000737:chemistry* / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: C492788:1-palmitoyl-2-hydroxy-sn-glycero-3-(phospho-RAC-(1-glycerol)); D005989:Glycerides; D008024:Ligands; D008823:Micelles; D010446:Peptide Fragments; D051964:Receptors, Mating Factor; C498031:STE2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins