Figure 4.

Schematic depiction of the PLA-based toroidal model for AC translocation. We hypothesize that in situ generation of non-lamellar lysophospholipids by the ACT-PLA activity on plasma membrane phospholipids would form a hydrophilic lipid pore of the toroidal architecture through which the AC domain transfer could directly take place. Such a hydrophilic lipidic pore might be of proteolipidic nature, this is, with the pore walls likely constituted by both lipids and one, or perhaps more, helices of the pore-forming region of ACT. The different structural elements are not drawn to scale. Colours used: In light blue, the whole hydrophobic domain which has been represented as a single big helical element; in dark blue, the RTX domain; in red, the linker segment, in which the two longer helices have been depicted; and in green, the AC domain, once in the cytosol.