Structure of yNAGK lacking its DUF619 domain.

<p>Cartoon representation of (A) the tetramer of truncated yNAGK, as observed in the crystal soaked with arginine (2.1 Å resolution); and (B), of the hexamer of <i>P. aeruginosa</i> NAGK (PDB file 2BUF <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034734#pone.0034734-RamnMaiques2" target="_blank">[7]</a>). Two different hues of blue, green or red were used to identify the two subunits forming each R dimer. NAG and arginine in (A), and NAG and ADP-Mg in (B) are shown in space-filling representation. In (A) the N- and C-lobes and the secondary structure elements are labeled (helices with letters, strands with numbers) in the arginine-containing subunit, except helix B, which is labeled in the left-hand adjacent subunit. The 2-fold axes (labeled in (A) as P, Q and R) are shown as broken blue lines ending in blue ellipses, and the 3-fold axis of hexameric NAGK (B) is shown as a blue triangle. Interdimeric junctions are labeled and enclosed in broken-line rectangles in both (A) and (B). One such junction for the hexameric enzyme is enlarged in the lower inset of (B). In turn, the intersubunit junctions in the R dimer are enclosed in dotted-line rectangles, and they are illustrated in the top insets for (A) and (B), after 90° rotation around the R axes, relative to the main <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034734#pone-0034734-g003" target="_blank">figures 3A and 3B</a>. In the insets, elements from the two subunits are differentiated by the color code and also by placing asterisks on the labeled elements of one subunit. (C) Stereo view of the intersubunit bonds in the R dimer involving the β5 strands and the C-terminal moiety of helix C. This figure illustrates the β-sheet continuity across the intersubunit interface through side-chain bonds. Elements from one subunit are yellow and those from the other are green.