Binding Site Geometry and Subdomain Valency Control Effects of Neutralizing Lectins on HIV-1 Viral Particles.
Carbohydrate binding proteins such as griffithsin, cyanovirin-N, and BanLec are potent HIV entry inhibitors and promising microbicides. Each binds to high-mannose glycans on the surface envelope glycoprotein gp120, yet the mechanisms by which they engage viral spikes and exhibit inhibition constants ranging from nanomolar to picomolar are not understood. To determine the structural and mechanistic basis for recognition and potency, we selected a panel of lectins possessing different valencies per subunit, oligomeric states, and relative orientations of carbohydrate binding sites to systematically probe their contributions to inhibiting viral entry. Cryo-electron micrographs and immuno gold staining of lectin-treated viral particles revealed two distinct effects-namely, viral aggregation or clustering of the HIV-1 envelope on the viral membrane-that were dictated by carbohydrate binding site geometry and valency. "Sandwich" surface plasmon resonance experiments revealed that a second binding event occurs only for those lectins that could aggregate viral particles. Furthermore, picomolar Kdvalues were observed for the second binding event, providing a mechanism by which picomolar IC50values are achieved. We suggest that these binding and aggregation phenomena translate to neutralization potency.
Laboratory of Bioorganic Chemistry, ‡Laboratory of Cell and Molecular Biology and #Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Center Drive, Bethesda, Maryland 20892, United States.
Sabrina
S
Lusvarghi
Laboratory of Bioorganic Chemistry, ‡Laboratory of Cell and Molecular Biology and #Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Center Drive, Bethesda, Maryland 20892, United States.
Katheryn
K
Lohith
Laboratory of Bioorganic Chemistry, ‡Laboratory of Cell and Molecular Biology and #Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Center Drive, Bethesda, Maryland 20892, United States.
Jeanne
J
Morin-Leisk
Laboratory of Bioorganic Chemistry, ‡Laboratory of Cell and Molecular Biology and #Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Center Drive, Bethesda, Maryland 20892, United States.
Rodolfo
R
Ghirlando
Laboratory of Bioorganic Chemistry, ‡Laboratory of Cell and Molecular Biology and #Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Center Drive, Bethesda, Maryland 20892, United States.
Jenny E
JE
Hinshaw
Laboratory of Bioorganic Chemistry, ‡Laboratory of Cell and Molecular Biology and #Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Center Drive, Bethesda, Maryland 20892, United States.
Carole A
CA
Bewley
D001665:Binding Sites; D015699:HIV Envelope Protein gp120 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015658:HIV Infections / Q000378:metabolism / Q000821:virology*; D015497:HIV-1 / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D037102:Lectins / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D014771:Virion / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D015699:HIV Envelope Protein gp120; D037102:Lectins
HIV gp120 (gp120); cryo-electron microscopy (cryo-EM); electron microscopy (EM); envelope glycoprotein; multivalency; surface plasmon resonance (SPR)
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