Mimicking the Structure of the V3 Epitope Bound to HIV-1 Neutralizing Antibodies†

Amit Mor, Eugenia Segal, Brenda Mester, Boris Arshava, Osnat Rosen, Fa-Xiang Ding, Joseph Russo, Amnon Dafni, Fabian Schvartzman, Tali Scherf, Fred Naider, Jacob Anglister
2009 Biochemistry  
The third variable region (V3) of the HIV-1 envelope glycoprotein gp120 is a target for virus neutralizing antibodies. The V3 sequence determines whether the virus will manifest R5 or ×4 phenotypes and use the CCR5 or C×CR4 chemokine co-receptor, respectively. Previous NMR studies revealed that both R5-and ×4-V3 peptides bound to antibodies 0.5β and 447-52D form β-hairpin conformations with the GPGR segment at the turn. In contrast, in their free form, linear V3 peptides and a cyclic peptide
more » ... sisting of the entire 35-residue V3 loop were highly unstructured in aqueous solution. Herein we evaluated a series of synthetic disulfide constrained V3-peptides in which the position of the disulfide bonds, and therefore the ring size, was systematically varied. NMR structures determined for singly and doubly disulfide constrained V3-peptides in aqueous solution were compared with those found for unconstrained V3 JRFL and V3 IIIB peptides bound to 447-52D and to 0.5β, respectively. Our study indicated that cyclic V3 peptides manifested significantly reduced conformational space compared to their linear homologues and that in all cases cyclic peptides exhibited cross strand interactions suggestive of β-hairpin like structures. Nevertheless, the singly constrained V3-peptides retained significant flexibility and did not form an idealized p-hairpin. Incorporation of a second disulfide bond results in significant overall rigidity and in one case, a structure close to that of V3 MN peptide bound to 447-52D Fab was assumed and in another case a structure close to that formed by the linear V3 IIIB peptide bound to antibody 0.5β was assumed.
doi:10.1021/bi802308n pmid:19281264 pmcid:PMC2756766 fatcat:fuwva5pq7zh7zdlrqfpkmyjj4q