FIG 2.
Structure of the scFv PL-2/Spike2 complex and conservation within the epitope. (A) Structure of the scFv PL-2/Spike2 complex in cartoon view (left half) and surface representation (right half). The Spike2 dimer is colored in red and gray. The scFv PL-2 light chains (VL) are colored purple, and the scFv PL-2 heavy chains (VH) are colored blue. On the surface representation, the PL-2 epitope amino acids are colored yellow. The glycosylation site on the scFv PL-2 heavy chain Asn 88 is labeled (GlcNAc). (B) Surface representation of Spike2 showing that the epitope is comprised of four discontinuous amino acid segments of one protomer (in yellow) and amino acid D566 from the other protomer (in green). The PL-2 epitope footprint is shown on top, and the linear schematic of the spike domain is shown on the bottom. (C) Surface representation of Spike2 (top) and linear schematic of spike domain (bottom) with amino acids colored by conservation between serotypes HAstV-1-8 from red (strictly conserved) to white (not conserved). (D) Spike2 structure shown from various sides. One half of the dimer is gray, and the other half is colored by amino acid conservation, whereby conserved, strongly similar, weakly similar, and nonconserved amino acids are colored red, dark pink, light pink, and white, respectively. Patches (sites) of conserved residues that overlap the MAb PL-2 epitope are circled. (E) Sequence alignment of HAstV-1-8 CP spike domains. Extra amino acids in in HAstV-2 CP spike loop 1 are boxed in red. Conserved, strongly similar, weakly similar, and nonconserved amino acids are colored red, dark pink, light pink, and white, respectively. Alignments and mapping of conservation onto the structure were performed with the online ENDscript server. Blue boxes highlight epitope amino acids in Spike2 that interact with the antibody heavy chain. Purple boxes highlight epitope amino acids in Spike2 that interact with the antibody light chain. Black boxes highlight amino acids in Spike2 that interact with both the heavy and light chains. At the bottom of each box is a colored circle to further highlight its interaction with the antibody heavy chain, light chain, or both.