Figure 3.

A.) Structures of the E. coli Lrp (left) and P. furiosus LrpA (right) octamers revealing the disruption in symmetry in the former structure. Only three octamer interfaces remain in E. coli Lrp, bridging dimers EF and GH, AB and EF, and AB and CD. The B. subtilis LrpC and AsnC octamers show the same symmetry depicted for P. furiosus LrpA. B) Cartoon representations of the E. coli Lrp octamer (left) and the P. furiosus LrpA octamer (right). The 90° angles are exact for P. furiosus LrpA and E. coli AsnC, for which the asymmetric units are dimers.⁹,¹¹ Because the asymmetric unit in the B. subtilis LrpC crystal contains a full octamer, the two-fold and four-fold axes are noncrystallographic, and small deviations from the 90° octamer interface angles are present.¹¹