title: Solution structure of the hydrophilic region of HIV-1 encoded virus protein U (Vpu) by CD and 1H NMR spectroscopy.
abstract: The HIV-1 specific Vpu is a class I oligomeric membrane phosphoprotein of unknown structure and mechanism. The first experimental evidence for the position of secondary structural elements present in the hydrophilic C-terminal region of Vpu under various solution regimes is reported. CD data for nine overlapping 15 amino-acid fragments and 3 longer fragments indicate the presence of only transitory amounts of stable structure in aqueous solution alone, while with increasing trifluoroethanol content limiting structures were found indicating two helical segments in the hydrophilic region of Vpu. These limiting structures were more precisely defined from a detailed study of Vpu41-58, Vpu52-74 and Vpu63-81, by a combination of 2D 1H NMR spectroscopy, distance geometry, and restrained molecular dynamics and energy minimization calculations. Sets of low-energy conformations compatible with the quantitative NOE data indicate that Vpu41-58 has an alpha-helix from residues 42 to 50 while a second helix is found for Vpu52-74 from residues 57 to 69. Vpu63-81 shows only the presence of a single reverse turn at residues 74 to 77, without any evidence of helix, under the same conditions. From CD measurements the first helix extends back to residue 30 and is connected to the N-terminal anchor of Vpu. Thus the hydrophilic region of Vpu consists of two alpha-helices joined by a flexible region of 6 or 7 residues, which contains the phosphoacceptor sites of Vpu at positions 52 and 56. The second helix is followed by a single reverse turn and a flexible C-terminus.
authors.affiliation: Department of Molecular Structure Research, Institute of Biotechnological Research, Braunschweig, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Wray
authors.forename: T
authors.initials: T
authors.lastname: Federau
authors.forename: P
authors.initials: P
authors.lastname: Henklein
authors.forename: S
authors.initials: S
authors.lastname: Klabunde
authors.forename: O
authors.initials: O
authors.lastname: Kunert
authors.forename: D
authors.initials: D
authors.lastname: Schomburg
authors.forename: U
authors.initials: U
authors.lastname: Schubert
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D005815:Genetic Code; D018257:Helix-Loop-Helix Motifs; D054298:Human Immunodeficiency Virus Proteins; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010446:Peptide Fragments / Q000737:chemistry; D017433:Protein Structure, Secondary; D012995:Solubility; D012996:Solutions; D054334:Viral Regulatory and Accessory Proteins / Q000737:chemistry* / Q000235:genetics; D014867:Water / Q000737:chemistry; D000086082:Viroporin Proteins
chemical_list: D054298:Human Immunodeficiency Virus Proteins; D010446:Peptide Fragments; D012996:Solutions; D054334:Viral Regulatory and Accessory Proteins; D014867:Water; C514859:vpu protein, Human immunodeficiency virus 1; D000086082:Viroporin Proteins