Molecular Biology Of The Cell 6th Edition by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter

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0 The intracellular bacterial pathogen Salmonella typhimurium, which causes gastroenteritis, injects effector proteins to promote its invasion into nonphagocytic host cells by the trigger mechanism. S. typhimurium first stim- ulates membrane ruffling to promote invasion, and then suppresses membrane ruffling once invasion is complete. This behavior is mediated in part by injection of two effec- tor proteins: which promotes membrane ruffling and invasion, and SptP, which blocks the effects of Both effector proteins target the monomeric GTPase, Rac, which in its active form promotes membrane ruffling. How do you suppose and SptP affect Rac activity? How do you suppose the effects of and SptP are staggered in time if they are injected simultaneously?