Structure: the amphipathic helix

How 37 residues fold into a membrane-breaking tool

LL-37 has almost no fixed shape in water, then snaps into an amphipathic alpha-helix when it meets a membrane. This unit builds that structure residue by residue: the cationic and hydrophobic faces, the net positive charge, and the way LL-37 is carved out of hCAP-18 by proteolysis.

Structure is where every later mechanism starts. The same helix that grips a bacterial membrane is the one that can stress a human cell, so getting the shape right is getting the whole story right.