title: The conserved residue Arg46 in the N-terminal heptad repeat domain of HIV-1 gp41 is critical for viral fusion and entry.
abstract: During the process of HIV-1 fusion with the target cell, the N-terminal heptad repeat (NHR) of gp41 interacts with the C-terminal heptad repeat (CHR) to form fusogenic six-helix bundle (6-HB) core. We previously identified a crucial residue for 6-HB formation and virus entry--Lys63 (K63) in the C-terminal region of NHR (aa 54-70), which forms a hydrophobic cavity. It can form an important salt bridge with Asp121 (D121) in gp41 CHR. Here, we found another important conserved residue for virus fusion and entry, Arg46 (R46), in the N-terminal region of NHR (aa 35-53), which forms a hydrogen bond with a polar residue, Asn43 (N43), in NHR, as a part of the hydrogen-bond network. R46 can also form a salt bridge with a negatively charged residue, Glu137 (E137), in gp41 CHR. Substitution of R46 with the hydrophobic residue Ala (R46A) or the negatively charged residue Glu (R46E) resulted in disruption of the hydrogen bond network, breakage of the salt bridge and reduction of 6-HB's stability, leading to impairment of viral fusion and decreased inhibition of N36, an NHR peptide. Similarly, CHR peptide C34 with substitution of E137 for Ala (E137A) or Arg (E137R) also exhibited reduced inhibitory activity against HIV-1 infection and HIV-1-mediated cell-to-cell fusion. These results suggest that the positively charged residue R46 and its hydrogen bond network, together with the salt bridge between R46 and E137, are important for viral fusion and entry and may therefore serve as a target for designing novel HIV fusion/entry inhibitors.
authors.affiliation: Key Laboratory of Tropical Disease Control of MOE, Department of Biochemistry and The Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Xiaoyi
authors.initials: X
authors.lastname: Wang
authors.forename: Weiliang
authors.initials: W
authors.lastname: Xiong
authors.forename: Xiaochu
authors.initials: X
authors.lastname: Ma
authors.forename: Meili
authors.initials: M
authors.lastname: Wei
authors.forename: Yanxia
authors.initials: Y
authors.lastname: Chen
authors.forename: Lu
authors.initials: L
authors.lastname: Lu
authors.forename: Asim K
authors.initials: AK
authors.lastname: Debnath
authors.forename: Shibo
authors.initials: S
authors.lastname: Jiang
authors.forename: Chungen
authors.initials: C
authors.lastname: Pan
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D015700:HIV Envelope Protein gp41 / Q000737:chemistry / Q000502:physiology*; D006801:Humans; D006861:Hydrogen Peroxide; D008561:Membrane Fusion; D008969:Molecular Sequence Data; D020449:Repetitive Sequences, Amino Acid; D017386:Sequence Homology, Amino Acid
chemical_list: D015700:HIV Envelope Protein gp41; D001120:Arginine; D006861:Hydrogen Peroxide