biostudies-literatureHe LNational Institute of Allergy and Infectious DiseasesUS Department of EnergyDr. Miriam and Sheldon G. Adelson Medical Research FoundationNIAID NIH HHSBasic Energy SciencesBiological and Environmental ResearchOffice of ScienceNIHNIGMS NIH HHS168650https://www.ebi.ac.uk/biostudies/studies/S-EPMC11297672biostudies-literatureUnknown436(16)Engineered reverse hairpin constructs containing a partial C-heptad repeat (CHR) sequence followed by a short loop and full-length N-heptad repeat (NHR) were previously shown to form trimers in solution and to be nanomolar inhibitors of HIV-1 Env mediated fusion. Their target is the in situ gp41 fusion intermediate, and they have similar potency to other previously reported NHR trimers. However, their design implies that the NHR is partially covered by CHR, which would be expected to limit potency. An exposed hydrophobic pocket in the folded structure may be sufficient to confer the observed potency, or they may exist in a partially unfolded state exposing full length NHR. Here we examined their structure by crystallography, CD and fluorescence, establishing that the proteins are folded haJournal of molecular biologyStructure and Interactions of HIV-1 gp41 CHR-NHR Reverse Hairpin Constructs Reveal Molecular Determinants of Antiviral Activity.PMC11297672R01 GM129325DE-AC02-05CH11231R01-GM129325R21 AI1409041R01GM126218R01 GM126218P41 GM103311P30 GM124169P41-GM103311R21AI140904Weber LGupta SKristensen LGDrouin-Allaire CPetzold CJAllaire MHe LBarbu RHalacoglu CMcAndrew RGifford GRalston CYChen YGochin MLi KHfalseStructure and Interactions of HIV-1 gp41 CHR-NHR Reverse Hairpin Constructs Reveal Molecular Determinants of Antiviral Activity.Engineered reverse hairpin constructs containing a partial C-heptad repeat (CHR) sequence followed by a short loop and full-length N-heptad repeat (NHR) were previously shown to form trimers in solution and to be nanomolar inhibitors of HIV-1 Env mediated fusion. Their target is the in situ gp41 fusion intermediate, and they have similar potency to other previously reported NHR trimers. However, their design implies that the NHR is partially covered by CHR, which would be expected to limit potency. An exposed hydrophobic pocket in the folded structure may be sufficient to confer the observed potency, or they may exist in a partially unfolded state exposing full length NHR. Here we examined their structure by crystallography, CD and fluorescence, establishing that the proteins are folded ha2024-01-01T00:00:00Z2024 Aug2026-05-29T17:15:52.816Z2026-04-08T05:29:38.184ZS-EPMC112976723886609110.1016/j.jmb.2024.168650