title: Interaction between heptad repeat 1 and 2 regions in spike protein of SARS-associated coronavirus: implications for virus fusogenic mechanism and identification of fusion inhibitors.
abstract: BACKGROUND
  Studies on the fusion-inhibitory peptides derived from the heptad repeat 1 and 2 (HR1 and HR2) regions of the HIV-1 envelope glycoprotein gp41 provided crucial information on the viral fusogenic mechanism. We used a similar approach to study the fusogenic mechanism of severe-acute-respiratory-syndrome-associated coronavirus (SARS-CoV).
  
  
  METHODS
  We tested the inhibitory activity against infection of two sets of peptides corresponding to sequences of SARS-CoV spike protein HR1 and HR2 regions and investigated the interactions between the HR1 and HR2 peptides by surface plasmon resonance, sedimentation equilibration analysis, circular dichroism, native polyacrylamide-gel electrophoresis, size exclusion high-performance liquid chromatography, and computer-aided homology modelling and molecule docking analysis.
  
  
  RESULTS
  One peptide, CP-1, derived from the HR2 region, inhibited SARS-CoV infection in the micromolar range. CP-1 bound with high affinity to a peptide from the HR1 region, NP-1. CP-1 alone had low alpha-helicity and self-associated to form a trimer in phosphate buffer (pH 7.2). CP-1 and NP-1 mixed in equimolar concentrations formed a six-helix bundle, similar to the fusogenic core structure of HIV-1 gp41.
  
  
  CONCLUSIONS
  After binding to the target cell, the transmembrane spike protein might change conformation by association between the HR1 and HR2 regions to form an oligomeric structure, leading to fusion between the viral and target-cell membranes. At the prefusion intermediate state, CP-1 could bind to the HR1 region and interfere with the conformational changes, resulting in inhibition of SARS-CoV fusion with the target cells. CP-1 might be modifiable to increase its anti-SARS-CoV activity and could be further developed as an antiviral agent for treatment or prophylaxis of SARS-CoV infection.
authors.affiliation: Lindsley F Kimball Research Institute, New York Blood Center, New York, NY 10021, USA.
authors.forename: Shuwen
authors.initials: S
authors.lastname: Liu
authors.forename: Gengfu
authors.initials: G
authors.lastname: Xiao
authors.forename: Yibang
authors.initials: Y
authors.lastname: Chen
authors.forename: Yuxian
authors.initials: Y
authors.lastname: He
authors.forename: Jinkui
authors.initials: J
authors.lastname: Niu
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Escalante
authors.forename: Huabao
authors.initials: H
authors.lastname: Xiong
authors.forename: James
authors.initials: J
authors.lastname: Farmar
authors.forename: Asim K
authors.initials: AK
authors.lastname: Debnath
authors.forename: Po
authors.initials: P
authors.lastname: Tien
authors.forename: Shibo
authors.initials: S
authors.lastname: Jiang
mesh_terms: D019380:Anti-HIV Agents / Q000737:chemistry / Q000494:pharmacology; D002478:Cells, Cultured; D005591:Chemical Fractionation; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D015700:HIV Envelope Protein gp41 / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D008561:Membrane Fusion / Q000187:drug effects / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D009842:Oligopeptides / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D011487:Protein Conformation / Q000187:drug effects; D045473:Severe acute respiratory syndrome-related coronavirus / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D045169:Severe Acute Respiratory Syndrome / Q000188:drug therapy / Q000378:metabolism* / Q000517:prevention & control; D064370:Spike Glycoprotein, Coronavirus; D020349:Surface Plasmon Resonance; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D014760:Viral Fusion Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D019380:Anti-HIV Agents; C106243:CP-1 peptide; D015700:HIV Envelope Protein gp41; D008562:Membrane Glycoproteins; D009842:Oligopeptides; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; D014760:Viral Fusion Proteins