Construction of the haemagglutinin membrane glycoprotein of influenza virus at Three A decision. The haemagglutinin glycoprotein of influenza virus is a trimer comprising two structurally distinct areas: a triple-stranded coiled-coil of alpha-helices extends 76 A from the membrane and a globular area of antiparallel beta-sheet, which incorporates the receptor binding website and the variable antigenic determinants, is positioned…