Structural highlights
FunctionPublication Abstract from PubMedContractile injection systems (CISs) mediate cell-cell interactions and are widespread among bacteria and archaea. These phage tail-like macromolecular machines puncture their target by a tube that is propelled by a contractile sheath. The mechanism underlying CIS firing, which starts with target binding and ends with sheath contraction, remains unclear. Here, we investigate the extracellular CIS from Algoriphagus machipongonensis (AlgoCIS) by a multimodal cryo-electron microscopy approach and structure-guided engineering, which allowed us to arrest AlgoCIS in multiple intermediate states of firing. Together with the post-firing structure, our data suggest a stepwise firing mechanism involving all structural modules: signal propagation starts with the binding of the tail-fibers, followed by opening of the cage, an expansion of the baseplate iris, and resulting in sheath contraction and the release of cap adaptor. Our study will serve as a framework for understanding the firing mechanism of diverse CISs and will facilitate the engineering of CISs for biomedical applications. Stepwise firing mechanism of an extracellular contractile injection system.,Xu J, Ericson CF, Toenshoff ER, Pilhofer M Nat Commun. 2026 Apr 24. doi: 10.1038/s41467-026-72240-y. PMID:42031783[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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