title: Sequence-specific 1H-NMR assignments and folding topology of human CD59.
abstract: CD59 is a recently discovered cell-surface glycoprotein that restricts lysis by homologous complement and has limited sequence similarity to snake venom neurotoxins. This paper describes the first results of a two-dimensional NMR study of CD59 prepared from human urine. Nearly complete 1H-NMR assignments were obtained for the 77 amino acid residues and partial assignments for the N-glycan and the glycosylphosphatidylinositol (GPI) anchor. These results together confirm that the C-terminal residue of the mature protein is Asn 77 and that the urine-derived form retains the nonlipid part of the GPI anchor. The data further indicate that the GPI anchor and possibly the N-glycan are structurally inhomogeneous and suggest that the phospholipid present in the intact GPI anchor was removed by phosphatidylinositol-specific phospholipase-D. The folding topology of the protein was determined from NOE enhancements and slowly exchanging backbone amide protons and consists primarily of five extended strands (denoted beta 1-beta 5 in sequence order), arranged into separate two-stranded (beta 1 and beta 2) and three-stranded (beta 3-beta 5) antiparallel beta-sheets. The same folding topology is found in all of the snake venom neurotoxins whose structures have been determined. The region between the beta 4 and beta 5 strands has helical character, a feature that is not present in the neurotoxins but that is seen in the topologically similar wheat germ agglutinin.
authors.affiliation: MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
authors.forename: C M
authors.initials: CM
authors.lastname: Fletcher
authors.forename: R A
authors.initials: RA
authors.lastname: Harrison
authors.forename: P J
authors.initials: PJ
authors.lastname: Lachmann
authors.forename: D
authors.initials: D
authors.lastname: Neuhaus
mesh_terms: D015703:Antigens, CD / Q000737:chemistry*; D001483:Base Sequence; D018957:CD59 Antigens; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D006023:Glycoproteins / Q000737:chemistry*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008562:Membrane Glycoproteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship; D014556:Urine / Q000737:chemistry
chemical_list: D015703:Antigens, CD; D018957:CD59 Antigens; D006023:Glycoproteins; D008562:Membrane Glycoproteins