Structural intermediates in the low pH-induced transition of influenza hemagglutinin
Fig 5
Molecular basis of the pH-induced conformational changes of HA.
(A) Structure comparisons of the Helix As in neutral and low pH conformations. Left: Ribbon diagrams showing the position of Helix A in the stem region. Helix A is colored red. Right: Zoomed-in views showing the Helix As in neutral (red) and low pH (yellow) conditions. The ribbons of the stem are colored dark gray for the neutral pH conformation and blue for the low pH conformation. (B) Structure comparisons of the neutral pH (cornflower blue), low pH intermediate (hot pink) and postfusion (green, PDB accession: 1HTM) HA central helices. The linker conducting helix to loop conformational change in the post-fusion transition is colored orange. (C) A schematic diagram illustrating the low pH-induced structural transition of HA.