C596 in the HN C-terminal extension mediates NA domain dimerization.

<p>(A) HN Ulster WT NA domain and HN C596S NA domain were expressed and purified as described in Methods and analyzed by SDS-PAGE under reducing and non-reducing conditions. The gel was stained with Coomassie Brilliant Blue. (B) Sucrose density gradient sedimentation and SDS-PAGE (non-reducing conditions) of Ulster HN NA domain and HN C596S NA domain proteins. (C) EM of WT Ulster HN NA domain, indicates the protein consists primarily of dimers, and the HN C596S NA domain, consists mostly as monomers.