9ux8

CryoEM Structure of LmuAB Apo State

spinqualitylabelsall models 9ux8, resolution 3.71Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 9ux8 is a 3 chain structure with sequence from Unclassified Bacillus (in: Bacteria). Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 3.71Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed Bacteria have developed a variety of immune systems to combat phage infections. The Lamassu system is a prokaryotic immune system with a core conserved structural maintenance of chromosomes (SMC) superfamily protein LmuB and diverse effectors named LmuA, whose mechanism remains unclear. Here we present a series of cryo-electron microscopy structures of the type-I Lamassu complex from Bacillus cellulasensis and the type-II Lamassu complex from Vibrio cholerae, both in apo and dsDNA-bound states, revealing an unexpected stoichiometry and topological architecture distinct from canonical SMC complexes. Combined structural and biochemical analyses show how the nuclease effector LmuA is sequestered in an inactive monomeric form within the Lamassu complex and, upon sensing foreign DNA ends, dissociates and assembles into an active tetramer capable of DNA cleavage. Our findings elucidate the mechanism by which Lamassu systems detect viral replication and implement antiphage defense, highlighting the roles of SMC proteins in prokaryotic immunity. Structural insights into type-I and type-II Lamassu antiphage systems.,Li M, Zhao X, Zhao X, Li D, Xiong W, Gao Z, Huang L, An L, Gao Y, Li S, Feng Y, Zhang K, Zhang Y Nat Chem Biol. 2026 Jan 2. doi: 10.1038/s41589-025-02102-z. PMID:41482579 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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