Fig. 3: Structure of the MaeB PTA hexamer and interactions with acetyl-CoA.
From: A rotary mechanism for allostery in bacterial hybrid malic enzymes
A Structural features of the D3 MaeBPTA hexamer, viewed from front, side and edge orientations. The classical PTA dimer (e.g. orange and blue protomers) trimerizes to give d1:d1, d2:d2 and d1:d2 interfaces. The N-terminal connection to the (missing) ME domain is situated at the hexamer long edge. B Interaction of the MaeBPTA domain with the regulatory acetyl-CoA ligand (yellow). A helical motif, which we term the 3′ loop (R535 and K538), interacts at the ligand 3′ phosphate. C Features of the PTA dimer unit (from two orthogonal views), which associates around the d2:d2 interface, and binds two molecules of acetyl-CoA at the d1:d2 cleft. D, E Involvement of the 3′ loop in forming the trimer interface, acetyl-CoA shown in vdw form. Two 3′ loops form the inner “cradle” at the d1:d1 interface, such that two acetyl-CoA binding sites come into close contact between separate dimers. F Cutaway view of the d1 face helix forming a flat surface for acetyl-CoA interaction.
