The inhibitory C-terminal extension forms a well-defined structure in crystals of the Ulster NA domain.

Abstract

<p>(A) Crystal structure of the Ulster HN NA domain dimer, shows a dimer-of-dimers tetramer. The C-terminal extension is highlighted in dark blue and red in each pair of dimers. (B) The Ulster HN dimer is shown, with the C-terminal extension in dark blue. The C-terminal extension begins at the base of the β-propeller domain, extends along the outside of the dimer interface, and then rises above the active site before inserting the C-terminus into the receptor-binding site.</p