Additionally, natural bond orbitals (NBO) analysis indicates an electronic delocalization between the two subunits in the dimer.
The X-ray structure at 2.4 Å resolution of the TorD dimer reveals extreme domain swapping between the two subunits.
Most of the interactions the three molecules are forming with the proteins are with the intersecting helices between the two subunits of the enzymes.
The difference between the energy gaps and distance between the two subunits {Re6} also suggests different resistance of the molecular complexes [26].
This phenomenon is likely to be caused by the close contact between the two subunits, enforced by interactions between their respective extracellular, 7-TM, and cytosolic regions (Kniazeff et al., 2011).
The absorption spectrum of the bistetracene is identical to that of the sum of their monomeric counterparts, which suggests that the ground-state interaction between the two subunits is weak.
Three classes of positive modulator, the benzamides, the thiadiazides, and the biarylsulfonamides differentially occupy a solvent accessible binding pocket at the interface between the two subunits that form the AMPA receptor ligand-binding pocket.
The large overall interface area (∼2500 Å2) of intersubunit bridges B2a, B3, and B5, and the inherent flexibility in regions connecting the contact residues are consistent with these bridges serving as anchoring patches for the ratcheting and rolling motions between the two subunits during translocation.
A noncrystallographic dyad exists between the two subunits in both hMtb-BirA and dhMtb-BirA structures.
The rmsds between the two subunits of dhMtb-BirA are 0.887 Å for 198 Cα equivalent atoms as opposed to the rmsds of 0.578 Å for 208 Cα pairs of the hMtb-BirA subunits.
Low resolution as well as variable domain movement between the two subunits in the asymmetric unit were limiting factors in applying non-crystallographic symmetry based refinement using REFMAC [35].
