Fig. 1.

Biochemical and EM analysis of WT and S92C mutant NDV HN proteins. (A) Schematic diagram of the NDV HN ectodomain construct and predicted α-helical regions. The black bars indicate the predicted α-helix positions. (B) WT HN migrates as a mixture of dimers and monomers in gel filtration experiments. (C) The S92C mutant migrates primarily as dimers on gel filtration columns. (D) EM pictures of WT and (E) S92C proteins. The red circles indicate potential dimers, and the black circles indicate potential tetramers.