Centre for Protein Science, Design and Engineering, Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India.
Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India.
Mol Microbiol. 2021 Apr;115(4):508-525. doi: 10.1111/mmi.14631. Epub 2020 Nov 11.
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.
β-桶状孔形成毒素通过形成寡聚β-桶状孔来破坏细胞膜。最关键的步骤是形成跨膜β-桶状支架的孔形成基序的膜插入。调节这些孔形成基序在β-桶状孔形成过程中结构重排的分子机制仍然难以捉摸。使用霍乱弧菌细胞溶素作为β-桶状孔形成毒素的典型例子，我们表明，孔形成基序铰链区域中的关键酪氨酸残基（Y321）在该过程中起着关键作用。Y321 突变会破坏膜结合毒素原聚体的寡聚化，并阻止随后的孔形成步骤。我们的研究表明，孔形成基序铰链区域中存在 Y321 对于毒素分子感知膜结合以及触发随后的寡聚化和孔形成过程所需的基本结构重排至关重要。霍乱弧菌细胞溶素通过这种机制形成孔，在结构上相关的β-桶状孔形成毒素中以前没有记录过。
