Abstract
Peptides derived from N-terminal heptad repeat (NHR) of the HIV-1 gp41 are generally poor inhibitors of HIV-1 entry, because they tend to aggregate and do not form a trimeric coiled-coil. In this study, we have fused portions of gp41 NHR, e.g. N36 or N28, to the T4 fibritin trimerization domain, Foldon (Fd), thus constructing novel NHR trimers, designated N36Fd or N28Fd, which could be expressed in Escherichia coli cells. The purified N36Fd and N28Fd exhibited SDS-resistant trimeric coiled-coil conformation with improved alpha-helicity compared with the corresponding N-peptides. They could interact with a C-peptide (e.g. C34) to form stable six-helix bundle and possessed potent anti-HIV-1 activity against a broad spectrum of HIV-1 strains. N28Fd was effective against T20-resistant HIV-1 variants and more resistant to proteinase K compared with T20 (enfuvirtide), a C-peptide-based HIV fusion inhibitor. Therefore, N28Fd trimer has great potentials for further development as an affordable therapeutic or microbicide for treatment and prevention of HIV-1 infection.
Highlights
Similar to the values of N28Fd trimer and N36Fd trimer, the f/f0 of N28FdϩC34 is between 1.6 and 1.9 (Table 1), which is in agreement with the moderately elongated shape of a 6-HB
T20 showed IC50 values of 3.4 nM against Bal and 1.75 nM against 93IN101 in these two assays. These results suggest that N36Fd and N28Fd trimers, like T20, have a broad spectrum antiviral activity against HIV-1, irrespective of coreceptor usage
T20 retained only 17% of the original amount (Fig. 8A) and completely lost its anti-HIV-1 activity after 3-h treatment with proteinase K (Fig. 8B). These results suggest that the N28Fd trimer is considerably more resistant to proteinase K than T20
Summary
Similar to the values of N28Fd trimer and N36Fd trimer, the f/f0 of N28FdϩC34 is between 1.6 and 1.9 (Table 1), which is in agreement with the moderately elongated shape of a 6-HB. Multiple peaks appeared in the result of SVA of N36FdϩC34, suggesting that several species with different molecular shapes may exist in the mixture. In such cases, fitting data using the measured f/f0, the weight average of the frictional ratio of molecular species present in solution, may lead to considerable errors [34]. A possible explanation for the deviation of the obtained molecular weights of the two major peaks of N36FdϩC34 from their calculated weights is the presence of multiple species, such as monomeric and dimeric 6-HB, in the solution
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