Fig. 4: Conformational change between the bound and apo forms of the MaeB PTA domain.
From: A rotary mechanism for allostery in bacterial hybrid malic enzymes
A Overlay of the acetyl-CoA PTAbound (non-transparent) and PTAapo (transparent) structures, viewed from front and side. The d2:d2 dimer interface at the triangle middle edge acts as a stator where the d1 subdomain flexes relative to this, driven by shifts at the ligand-sensing 3′ loop at the d1:d1 interface (helix labelled i1 contributing Y494 and R497). B Demonstration of flexation in a single PTA monomer, from two orthogonal views. Acetyl-CoA “attracts” the 3′ loop, reducing the d1:d2 distance in the bound state (yellow d1/orange d2) relative to the apo form (light blue d1/dark blue d2). The d1 subdomain “rocker” movement (labelled d1 flex) transmits ligand occupancy at the 3′ loop to the interface (i1). Importantly the PTA N-terminal helix (linking to ME domain in full-length protein) shifts between the two states. C Zoomed-in view of isolated PTAapo and PTAbound d1:d1 interfaces, viewed from same orientation as that in (A) superimposition above. The interface helices shear relative to one another as the hexamer flexes, altering interactions between Y494, R497 and H517.
