Bacteria and the organisms they parasitize are engaged in a constant struggle. Each side possesses a veritable arsenal of weapons and defensive countermeasures. One of the most potent weapons systems that bacteria use is the type Ⅲ secretion system, which injects certain bacterial proteins into adjacent host cells. The proteins selected by the secretion machinery often resemble the host's own proteins, so they can switch off defensive systems and turn the cells into puppets of a bacterial master. In this issue, Akeda and Galan (page 911) give us a first peek into the loading mechanism of the bacterial type Ⅲ secretion system. The crystal structures of proteins that are transported by the type Ⅲ secretion machine have been solved. The diameter of the conduit these proteins must travel has also been ascertained. A paradox emerges when these data are compared - the proteins are too large to travel through the secretory apparatus. So how do bacteria get the camel to pass through the eye of a needle? A solution suggested by Akeda and Galan implicates InvC, an essential component of the Salmonella enterica type Ⅲ machinery.
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