Tyrosine in the hinge region of the pore-forming motif regulates oligomeric β-barrel pore formation by Vibrio cholerae cytolysin

Abstract

β‐barrel pore‐forming toxins perforate cell membranes by forming oligomeric β‐barrel pores. The most crucial step is the membrane‐insertion of the pore‐forming motifs that create the transmembrane β‐barrel scaffold. Molecular mechanism that regulates structural reorganization of these pore‐forming motifs during β‐barrel pore‐formation still remains elusive. Using Vibrio cholerae cytolysin as an archetypical example of the β‐barrel pore‐forming toxin, we show that a key tyrosine residue (Y321) in the hinge region of the pore‐forming motif plays crucial role in this process. Mutation of Y321 abrogates oligomerization of the membrane‐bound toxin protomers, and blocks subsequent steps of pore‐formation. Our study suggests that the presence of Y321 in the hinge region of the pore‐forming motif is crucial for the toxin molecule to sense membrane‐binding, and to trigger essential structural rearrangements required for the subsequent oligomerization and pore‐formation process. Such a regulatory mechanism of pore‐formation by V. cholerae cytolysin has not been documented earlier in the structurally related β‐barrel pore‐forming toxins.