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.
PLoS One. 2012;7(9):e44874. doi: 10.1371/journal.pone.0044874. Epub 2012 Sep 7.
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.
在 HIV-1 与靶细胞融合的过程中，gp41 的 N 端七肽重复（NHR）与 C 端七肽重复（CHR）相互作用形成融合六螺旋束（6-HB）核心。我们之前确定了 6-HB 形成和病毒进入的关键残基——NHR（aa54-70）C 端区域的 Lys63（K63），它形成一个疏水性腔。它可以与 gp41 CHR 中的 Asp121（D121）形成重要的盐桥。在这里，我们发现 NHR N 端的另一个对病毒融合和进入很重要的保守残基——Arg46（R46）（aa35-53），它与 NHR 中的极性残基 Asn43（N43）形成氢键，作为氢键网络的一部分。R46 还可以与 gp41 CHR 中的带负电荷的残基 Glu137（E137）形成盐桥。用疏水性残基 Ala（R46A）或带负电荷的残基 Glu（R46E）取代 R46，会破坏氢键网络，破坏盐桥，降低 6-HB 的稳定性，从而损害病毒融合，并降低 NHR 肽 N36 的抑制作用。同样，用 Ala（E137A）或 Arg（E137R）取代 CHR 肽 C34 中的 E137，也表现出对 HIV-1 感染和 HIV-1 介导的细胞间融合的抑制活性降低。这些结果表明，带正电荷的残基 R46 及其氢键网络，以及 R46 和 E137 之间的盐桥，对病毒融合和进入很重要，因此可能成为设计新型 HIV 融合/进入抑制剂的靶点。
