A solution NMR study of the interactions of oligomannosides and the anti-HIV-1 2G12 antibody reveals distinct binding modes for branched ligands.
The structural and affinity details of the interactions of synthetic oligomannosides, linear (di-, tri-, and tetra-) and branched (penta- and hepta-), with the broadly neutralizing anti-HIV-1 antibody 2G12 (HIV=human immunodeficiency virus) have been investigated in solution by using ligand-based NMR techniques, specifically saturation transfer difference (STD) NMR spectroscopy and transferred NOE experiments. Linear oligomannosides show similar binding modes to the antibody, with the nonreducing terminal disaccharide Manα(1→2)Man (Man=mannose) making the closest protein/ligand contacts in the bound state. In contrast, the branched pentamannoside shows two alternate binding modes, involving both ligand arms (D2- and D3-like), a dual binding description of the molecular recognition of this ligand by 2G12 in solution that differs from the single binding mode deduced from X-ray studies. On the contrary, the antibody shows an unexpected selectivity for one arm (D1-like) of the other branched ligand (heptamannoside). This result explains the previously reported lack of affinity enhancement relative to that of the D1-like tetramannoside. Single-ligand STD NMR titration experiments revealed noticeable differences in binding affinities among the linear and branched ligands in solution, with the latter showing decreased affinity. Among the analyzed series of ligands, the strongest 2G12 binders were the linear tri- and tetramannosides because both show similar affinity for the antibody. These results demonstrate that NMR spectroscopic techniques can deliver abundant structural, dynamics, and affinity information for the characterization of oligomannose-2G12 binding in solution, thus complementing, and, as in the case of the pentamannoside, extending, the structural view from X-ray crystallography. This information is of key importance for the development of multivalent synthetic gp120 high-mannose glycoconjugate mimics in the context of vaccine development.
Laboratory of GlycoNanotechnology, Biofunctional Nanomaterial Unit, CIC biomaGUNE, Parque Tecnológico, Paseo de Miramón 182, 20009 San Sebastián, Spain.
Pedro M
PM
Enríquez-Navas
Marco
M
Marradi
Daniel
D
Padro
Jesús
J
Angulo
Soledad
S
Penadés
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000276:immunology; D001666:Binding Sites, Antibody; D000080908:Broadly Neutralizing Antibodies; D002240:Carbohydrate Sequence; D018360:Crystallography, X-Ray; D006001:Glycoconjugates / Q000737:chemistry* / Q000276:immunology; D015483:HIV Antibodies / Q000737:chemistry* / Q000276:immunology; D015699:HIV Envelope Protein gp120 / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D015497:HIV-1 / Q000737:chemistry* / Q000276:immunology; D006801:Humans; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009844:Oligosaccharides / Q000737:chemistry*; D025942:Oligosaccharides, Branched-Chain / Q000737:chemistry*
C529157:2G12 monoclonal antibody; D000911:Antibodies, Monoclonal; D000080908:Broadly Neutralizing Antibodies; D006001:Glycoconjugates; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120; D008024:Ligands; D009844:Oligosaccharides; D025942:Oligosaccharides, Branched-Chain; C028569:oligomannoside