Fig. 3: ADI-15946 binds a highly conserved epitope shielded by the mobile β17–β18 loop of the glycan cap. | Nature Structural & Molecular Biology

Fig. 3: ADI-15946 binds a highly conserved epitope shielded by the mobile β17–β18 loop of the glycan cap.

From: Structural basis of broad ebolavirus neutralization by a human survivor antibody

Fig. 3

a, Structures show that ADI-15946 (orange, left) binds the hydrophobic 310 pocket of GP (teal) that is usually occupied by the β17–β18 loop of the glycan cap (green, middle). Right, binding NPC1 loop C (magenta) to GP induces a conformational change in which the GP1 310 helix unwinds and asparagine 73 (N73) becomes solvent exposed while GP2 lysine 510 (K510) inserts into the cavity left behind after the unwinding of the 310 helix. ADI-15946 may prevent these conformational changes from occurring by locking down the 310 helix with residues that mimic those of the β17–β18 loop. b, An enlarged view of the 310 pocket shows that CDR H3 of ADI-15946 positions similar residues in similar orientations to that of the β17–β18 loop. c, Neutralization assay showing that ADI-15946 has enhanced neutralization of a GP construct lacking the β17–β18 loop compared to wild type (WT), probably due to increased access to the 310 pocket. Data are mean ± s.d., n = 6 biologically independent samples. d, Binding assays showing that a point mutation in the β17–β18 loop (W291R) results in enhanced binding to rVSV-EBOV GP in an ELISA. Data are mean ± s.d., n = 4 biologically independent samples. e, Neutralization assays showing that the W291R mutation in the β17–β18 loop or its proteolytic removal (CL) enhance the capacity of ADI-15946 to neutralize rVSV-EBOV GP. Data are mean ± s.d., n = 6 biologically independent samples. f, Kinetic binding studies by biolayer interferometry reveal enhanced association rate and slower dissociation rate of ADI-15946 to GPCL compared to uncleaved GP.