File:H-mediated membrane binding and fusion between the viral and endosomal membranes..png

Figure 4. HA-mediated membrane binding and fusion between the viral and endosomal membranes. (A) H1 (blue) binding to a moiety containing sialic acid group on the plasma membrane (light green); (B) After a reduction in pH in the endosome, H2 undergoes a conformational change that drives the fusion peptides (red) into the host cell membrane; (C) A further conformational change brings the outermost leaflets of the opposing membranes together to form a stalk (D), where it is thought to be the action of several fusogenic HA2 working in concert. The dashed lines divide the upper and lower leaflets of the membranes for clarity.Figure adapted from the Protein Data Bank