Field-driven peptide transport across the inner mitochondrial membrane via a transient membrane pore.

Cell-penetrating peptides translocate across a membrane via different mechanisms. In this work, we employ coarse-grained molecular dynamics simulations to study the effect of an external electric field, which mimics the transmembrane potential, on the stability of a mitochondrial membrane and the translocation of peptide(s) across it. In the absence of peptides, we observed that the membrane undulates under the applied field and develops a curvature promoted by the presence of cardiolipin, which further leads to the formation of a transient pore caused by the merging of the phospholipids from the upper leaflet into the lower leaflet. We also studied the translocation of two different mitomembrane-targeting peptides at various electric field intensities in which the integrity of the membrane was preserved. Under the applied field, we observed that the cationic residues of each peptide bound to the phosphate headgroups of lipids, gradually moving toward the membrane region where a transient pore forms at a critical field strength, followed by the translocation across the mitomembrane via this transient pore. Comparing systems containing single peptides with those containing ten peptides of each type, we found that the transport of multiple peptides across the mitomembrane requires lower field magnitudes, no more than two peptides translocate at a time, and the translocation time, once in the pore, is marginally higher for multiple peptides compared to a single peptide. Overall, the findings from this work enhance our understanding of the effect of the transmembrane potential on the transport of mitomembrane-targeting peptides.