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. Author manuscript; available in PMC: 2019 Feb 28.
Published in final edited form as: Chem Rev. 2018 Jan 10;118(4):1691–1741. doi: 10.1021/acs.chemrev.7b00305

Figure 9.

Figure 9

pH-dependent conformational transition of hemagglutinin. (a) In the prefusion form (Protein Data Bank entry 1JSD), HA2 Asp112 forms an ion pair with the N-terminal amino group, and HA2 Glu69 forms a salt bridge with HA1 Arg102. (b) In the postfusion form (PDB entry 1HTM), the N-terminus of the HA2 central helix extends from residue 74 to residue 37, while residues 106–113 (in cyan) become a loop, allowing the C-terminal helical segment (in blue) to fold back. HA2 Asp112 is now exposed on the surface, and Glu69 forms a pair with Glu74 of a neighboring chain.