Influenza virus haemagglutinin. Structural predictions suggest that the fibrillar appearance is due to the presence of a coiled-coil.

Predictions of secondary structure for the two chains HA1 and HA2 of the haemagglutinin from the Hong Kong influenza virus A/Memphis/102/72 reveal a striking contrast between the potential conformations of the two chains. HA1 is predicted to be rich in beta-structure while HA2 is highly helical. The predictions further suggest that coiled-coil type interactions between the central helical segments of the HA2 chains may hold the haemagglutinin monomers together in the virus.