Speaker
Description
Bacteria have evolved a number of diverse strategies to evade and resist phage infection, however the detailed mechanisms for many of these remain to be understood. In particular, fewer membrane associated anti-phage defence systems have been described in detail, especially ones functioning through a non-abortive mechanism. Here we investigate a two-protein defence system where one protein is predicted to be membrane associated and the other lacks any homology with known domains or existing structures. Using cryo-electron microscopy we show the predicted transmembrane protein forms a dimer, lacking any canonical membrane-spanning helices. Additionally, we obtained a high-resolution map of the two proteins in complex, revealing extensive conformational changes relative to the homodimer. Finally, we show a structure of the defence system bound to a nucleic acid, which allows us to speculate on the overall mechanism of direct defence of this previously undescribed system.
