Figure 7. Model of MakA pore formation.

a-c) Proposed pore assembly initiated from a trimer of dimers. The orientation of each asymmetric dimer building block relative to the symmetry axis changes as additional subunits are incorporated (indicated by the red line and arrow). d-f) Illustration of subunit rotation during pore growth. Following membrane insertion of MakA and/or MakE into the initial trimer of dimers, intermolecular interactions between neighboring assembly units drive progressive rotational and translational rearrangements that reorient subunits toward the pore axis, decreasing the angle between each building block and the central channel and promoting formation of an open transmembrane pore. In this model, MakB may remain associated with the soluble region or function outside the mature pore complex.