Sackett, K., and Y. as a model system. Furthermore, nonconserved substitutions of Asp632 significantly reduced the potency of C34 to sequestrate six-helix bundle formation and to inhibit HIV-1-mediated cell-cell fusion and contamination, suggesting its importance for designing antiviral fusion inhibitors. Taken together, these data suggest that the salt bridge between the N- and C-terminal heptad repeat regions of the fusion-active HIV-1 gp41 core structure is critical for viral access and inhibition. Contamination with human immunodeficiency computer virus type 1 (HIV-1) is usually mediated by its envelope glycoprotein (Env), a type I transmembrane protein which is usually originally synthesized as the single, glycosylated, polyprotein precursor gp160 and subsequently cleaved Spectinomycin HCl by a cellular protease to yield gp120 and gp41 subunits (13, 14, 20, 46, 48). Upon binding of the HIV-1 Env surface subunit gp120 to the cell receptor CD4 and subsequently to a coreceptor (CCR5 or CXCR4), its transmembrane subunit gp41 is usually released to mediate fusion of viral and cellular membranes (20, 25, 54). Structurally, HIV-1 gp41 consists of extracellular, transmembrane, and cytoplasmic domains (Fig. ?(Fig.1A).1A). Its extracellular domain name (ectodomain) contains four major Spectinomycin HCl functional regions: a hydrophobic, glycine-rich fusion peptide; an N-terminal heptad repeat (NHR) (also called HR1), a C-terminal heptad repeat (CHR) (also called HR2), and a tryptophan-rich region. In the early 1990s, several peptides derived from the NHR (N peptides) and CHR (C peptides) were found to have potent anti-HIV activity (30, 43, 68, 69). Although their mechanism of action was not known at that time, the unprecedented anti-HIV Spectinomycin HCl activity of these peptides opened a new avenue for developing antiviral drugs. A C peptide known as T20 (brand name, Fuzeon) has been successfully developed as a novel class of anti-HIV drugs for clinical use (36, 37, 50). Open in a separate windows FIG. 1. Structure and function of the HIV-1 gp41 core. (A) Schematic view of the gp41 functional regions. FP, fusion peptide; S-S, disulfide bond loop; TM, transmembrane domain name; CT, cytoplasmic tail. The residue number for each region corresponds to its position in gp160 of HIV-1HXB2. (B) Crystal structure of the six-helix bundle Spectinomycin HCl modeled by the peptides N36 and C34. The N36 helices are green, whereas the C34 helices are reddish. (C) The salt bridge created by residues Lys574 in the NHR and Asp632 in the CHR. The obtaining of anti-HIV peptides also provided important information to explore the structure of the gp41 molecule. In 1995, Lu et al (42). recognized a stable, proteinase-resistant structure comprising Rabbit Polyclonal to Nuclear Receptor NR4A1 (phospho-Ser351) two peptides, N51 and C43, derived from a recombinant protein fragment of the gp41 ectodomain by using protein dissection experiments. N51 and C43 associate to form a stable, -helical trimeric complex of heterodimers, with N51 and C43 helices oriented in an antiparallel fashion (42). Further proteolysis of the N51/C43 complex resulted in the identification of the N36 and C34 peptides (43). Similarly, N36 and C34 form a stable -helical trimer of NHR-CHR heterodimers, whereas N36 alone is predominantly aggregated and C34 alone remains mostly unfolded (43). X-ray crystallographic studies by three impartial groups confirmed that this thermostable subdomain of HIV-1 gp41 folds into a -helical six-helix bundle, in which three NHR helices form an interior, parallel coiled-coil trimer while three CHR helices pack in an oblique, Spectinomycin HCl antiparallel manner into the highly.