CONFORMATIONAL MAPPING OF A VIRAL FUSION PEPTIDE IN STRUCTURE-PROMOTING SOLVENTS USING CIRCULAR-DICHROISM AND ELECTROSPRAY MASS-SPECTROMETRY

The N-terminal domain of human immunodeficiency virus (HIV)-1 glycopro tein 41,000 (FP; residues 1-23; NH2-AVGIGALFL-GFLGAAGSTMGARS-CONH2) is involved in the fusion and cytolytic processes underlying viral-cell infection. Here, we use circular dichroism (CD) spectroscopy, along wi th electrospray ionization (ESI) mass spectrometry and tandem (MS/MS) mass spectrometry during the course of hydrogen/deuterium exchange, to probe the local conformations of this synthetic peptide in two membra ne mimics. Since amino acids that participate in defined secondary str ucture (i.e., alpha-helix or beta-sheet) exchange amido hydrogens more slowly than residues in random structures, deuterium exchange was com bined with CD spectroscopy to map conformations to specific residues. For FP suspended in the highly structure-promoting solvent hexafluoroi sopropanol (HFIP), CD spectra indicated high alpha-helix and disordere d structures, whereas ESI and MS/MS mass spectrometry indicated that r esidues 5-15 were alpha-helical and 16-23 were disordered. For FP susp ended in the less structure-promoting solvent trifluoroethanol (TFE), CD spectra showed lower alpha-helix, with ESI and MS/MS mass spectrome try indicating that only residues 9-15 participated in the alpha-helix . These results compare favorably with previous two-dimensional nuclea r magnetic resonance studies on the same peptide, Proteins Suppl 2:38- 49, 1998. (C) 1998 Wiley-Liss, Inc.