Chemoenzymatic synthesis of HIV-1 gp41 glycopeptides:: Effects of glycosylation on the anti-HIV activity and α-helix bundle-forming ability of peptide C34

C34 is a 34-mer peptide derived from the C-terminal ectodomain of HIV-1 envelope glycoprotein, gp41. The C34 region in native gp41 carries a conserved N-glycon at Asn637 and the sequence is directly involved in the virus-host membrane fusion, an essential step for HIV-1 infection. This paper describes the synthesis of glycoforms of C34 which carry a monosaccharide, a disaccharide, and a native oligosaccharide moiety. The synthesis of the glycopeptide which carries a native high-mannose type N-glycon was achieved by a chemoenzymatic approach by using an endogly-cosidose-catalyzed oligosaccharide transfer as the key step. The effects of glycosylation on the inhibitory activity and the helixbundle forming ability of C34 were investigated. It was found that glycosylation moderately decreases the anti-HIV activity of C34 and, in comparison with C34, glyco-C34 forms less compact six-helix bundles with the corresponding N-terminal peptide, N36. This study suggests that conserved glycosylation modulates the anti-HIV activity and conformations of the gp41 C-peptide, C34.