title: Solution conformational preferences of immunogenic peptides derived from the principal neutralizing determinant of the HIV-1 envelope glycoprotein gp120.
abstract: With standard one- and two-dimensional proton NMR techniques, a common structural motif has been identified in water solutions of short peptide sequences derived from the envelope glycoprotein gp120 of HIV-1. Three peptides of lengths 12, 24, and 40 residues (termed RP342, RP142, and RP70, respectively) were synthesized, each containing a central amino acid sequence common to many HIV-1 isolates. In addition, RP70 contained a disulfide bond between cysteine residues close to the ends of the molecule, forming a loop that is thought to constitute an important structural and immunological component of the intact glycoprotein. Peptides RP70 and RP142 showed evidence for the presence of a significant population of conformations containing a beta-turn in the conserved sequence Gly-Pro-Gly-Arg. Strong nuclear Overhauser effect (NOE) connectivities were observed between the amide protons of the arginine and the adjacent glycine. A weak NOE connectivity was observed between the C alpha H of the proline residue and the NH of the Arg [a d alpha N(i,i + 2) NOE connectivity], confirming the presence of a conformational preference for a turn conformation in this sequence. The remainder of the peptide showed evidence of conformational averaging: no NMR evidence for a uniquely folded structure was obtained for any of the peptides in water solution. Circular dichroism (CD) spectra indicated that no ordered helix was present in water solutions of RP70, although a CD spectrum that indicated the presence of approximately 30% helix could be induced by the addition of trifluoroethanol.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, California 92037.
authors.forename: K
authors.initials: K
authors.lastname: Chandrasekhar
authors.forename: A T
authors.initials: AT
authors.lastname: Profy
authors.forename: H J
authors.initials: HJ
authors.lastname: Dyson
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D004220:Disulfides / Q000737:chemistry; D015488:HIV Antigens / Q000737:chemistry*; D015699:HIV Envelope Protein gp120 / Q000737:chemistry* / Q000276:immunology; D015497:HIV-1 / Q000276:immunology*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D012996:Solutions; D012997:Solvents; D013696:Temperature
chemical_list: D004220:Disulfides; D015488:HIV Antigens; D015699:HIV Envelope Protein gp120; D010455:Peptides; D012996:Solutions; D012997:Solvents