Length matters: Functional flip of the short TatA transmembrane helix.

The twin arginine translocase (Tat) exports folded proteins across bacterial membranes. The putative pore-forming or membrane-weakening component (TatA in B. subtilis) is anchored to the lipid bilayer via an unusually short transmembrane α-helix (TMH), with less than 16 residues.

Structural and functional characterization of the pore-forming domain of pinholin S68.

Pinholin S68 triggers the lytic cycle of bacteriophage φ21 in infected Activated transmembrane dimers oligomerize into small holes and uncouple the proton gradient. Transmembrane domain 1 (TMD1) regulates this activity, while TMD2 is postulated to form the actual "pinholes." Focusing on the TMD2 fragment, we used synchrotron radiation-based circular dichroism to confirm its α-helical conformation and transmembrane alignment.