1 research outputs found
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 effectsî—¸namely, viral
aggregation or clustering of the HIV-1 envelope on the viral membraneî—¸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 <i>K</i><sub>d</sub> values were
observed for the second binding event, providing a mechanism by which
picomolar IC<sub>50</sub> values are achieved. We suggest that these
binding and aggregation phenomena translate to neutralization potency