Overall structure.

A: Cartoon representation of the HiNagB hexamer. Each monomer is colored differently. The protein is a trimer of dimers and the orientation shows three subunits at the bottom and three at the top. The black box is the dimer interface. B: Cartoon representation of the PmNagB dimer. Each monomer is colored as a rainbow–with the N-terminus in Blue and the C-terminus in Red. The black box is the dimer interface. C: The zoomed-up area of the dimer interface–the area that is approximately marked in the black box. One of the subunits of PmNagB is superposed on one of the subunits of HiNagB (the green subunit in 3A). Notice that the overlapped subunits superpose well, but the other monomer of the dimer is shifted. D: The interaction of the residues in the dimer interface. There are several main chain hydrogen bonds.