Figure 3

Oligomeric assembly of SA1388. (A) Schematic of an SA1388 dimer showing the dimer interface between the two NIF3 domains (NIF3-N and NIF3-C). The helices of monomer A are shown in blue and that of monomer B are in cyan. Similarly, the strands from monomer A are in yellow and that of monomer B in green. The strands are numbered according to the legend in Figure 1A. The two PII domains are shown in gray and the bound zinc atoms shown as orange balls. The domain-swapped β-strand (β16), that crosses over into the other subunit is highlighted in red. (B) Two orthogonal views of SA1388 trimers that make up half of the hexamer. The monomers are colored blue, green and orange respectively and the three domains are labelled. (C) Superimposed structures of SA1388 PII domain trimer (the three monomers are colored red, blue and violet, respectively) and that of E. coli glnK (PDB Id: 2GNK, colored gray). The four β strands in one SA1388 PII monomer are numbered according to the same scheme as in Figure 2B.