Class IB type III secretion system chaperone protein, similar to Shigella flexneri Spa15
This family includes type III secretion system (T3SS) chaperone proteins similar to Shigella flexneri Spa15, Salmonella enterica InvB, and similar proteins. In S. flexineri, which is a facultative intracellular pathogen that invades the colonic epithelium and causes bacillary dysentery, the T3SS allows injection of a number of effectors to ensure their stabilization prior to secretion. Spa15 is the chaperone for several TTS effectors, including IpaA, IpgB1, OspC3, OspB and OspD1. Effector IpgB that chaperone Spa15 is a mimic of the human Ras-like Rho guanosine triphosphatase RhoG, thus activating Rac1 guanosine triphosphatase and setting off membrane ruffling of the cell, assisting the internalization of Shigella. Also, Spa15 is a chaperone for secreted anti-activator OspD1 which is involved in the control of transcription by the type III secretion apparatus (T3SA) activity in Shigella flexneri.
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