The C34 Peptide Fusion Inhibitor Binds to the Six-Helix Bundle Core Domain of HIV-1 gp41 by Displacement of the C-Terminal Helical Repeat Region

Biochemistry. 2015 Nov 17;54(45):6796-805. doi: 10.1021/acs.biochem.5b01021. Epub 2015 Nov 9.


The conformational transition of the core domain of HIV-1 gp41 from a prehairpin intermediate to a six-helix bundle is responsible for virus-cell fusion. Several inhibitors which target the N-heptad repeat helical coiled-coil trimer that is fully accessible in the prehairpin intermediate have been designed. One such inhibitor is the peptide C34 derived from the C-heptad repeat of gp41 that forms the exterior of the six-helix bundle. Here, using a variety of biophysical techniques, including dye tagging, size-exclusion chromatography combined with multiangle light scattering, double electron-electron resonance EPR spectroscopy, and circular dichroism, we investigate the binding of C34 to two six-helix bundle mimetics comprising N- and C-heptad repeats either without (core(SP)) or with (core(S)) a short spacer connecting the two. In the case of core(SP), C34 directly exchanges with the C-heptad repeat. For core(S), up to two molecules of C34 bind the six-helix bundle via displacement of the C-heptad repeat. These results suggest that fusion inhibitors such as C34 can target a continuum of transitioning conformational states from the prehairpin intermediate to the six-helix bundle prior to the occurrence of irreversible fusion of viral and target cell membranes.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Amino Acid Sequence
  • Binding Sites
  • Chromatography, Gel
  • Circular Dichroism
  • Electron Spin Resonance Spectroscopy
  • HIV Envelope Protein gp41 / chemistry
  • HIV Envelope Protein gp41 / metabolism*
  • HIV-1 / metabolism*
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Peptide Fragments / chemistry
  • Peptide Fragments / metabolism*
  • Protein Binding
  • Protein Conformation
  • Protein Interaction Mapping
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Repetitive Sequences, Amino Acid
  • Scattering, Radiation
  • Virus Internalization


  • HIV Envelope Protein gp41
  • Peptide Fragments
  • peptide C34