https://www.selleckchem.com/products/emd638683.html The type VI secretion system (T6SS) is a contractile nanomachine widely distributed among pathogenic and commensal Gram-negative bacteria. The T6SS is used for inter-bacterial competition to directly kill competing species; however, its importance during bacterial infection in vivo remains poorly understood. We report that the murine pathogen Citrobacter rodentium, used as a model for human pathogenic Escherichia coli, harbors two functional T6SSs. C. rodentium employs its T6SS-1 to colonize the murine gastrointestinal tract by targeting commensal Enterobacteriaceae. We identify VgrG1 as a C. rodentium T6SS antibacterial effector, which exhibits toxicity in E. coli. Conversely, commensal prey species E. coli Mt1B1 employs two T6SSs of its own to counter C. rodentium colonization. Collectively, these data demonstrate that the T6SS is a potent weapon during bacterial competition and is used by both invading pathogens and resident microbiota to fight for a niche in the hostile gut environment.Nav1.7 represents a preeminent target for next-generation analgesics for its critical role in pain sensation. Here we report a 2.2-Å resolution cryo-EM structure of wild-type (WT) Nav1.7 complexed with the β1 and β2 subunits that reveals several previously indiscernible cytosolic segments. Reprocessing of the cryo-EM data for our reported structures of Nav1.7(E406K) bound to various toxins identifies two distinct conformations of S6IV, one composed of α helical turns only and the other containing a π helical turn in the middle. The structure of ligand-free Nav1.7(E406K), determined at 3.5-Å resolution, is identical to the WT channel, confirming that binding of Huwentoxin IV or Protoxin II to VSDII allosterically induces the α → π transition of S6IV. The local secondary structural shift leads to contraction of the intracellular gate, closure of the fenestration on the interface of repeats I and IV, and rearrangement of the binding