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Mol Cell. 2000 Dec;6(6):1449-60.

Modulation of host signaling by a bacterial mimic: structure of the Salmonella effector SptP bound to Rac1.

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Section of Microbial Pathogenesis, Boyer Center for Molecular Medicine, Yale School of Medicine, New Haven, CT 06536, USA.


Salmonella spp. utilize a specialized protein secretion system to deliver a battery of effector proteins into host cells. Several of these effectors stimulate Cdc42- and Rac1-dependent cytoskeletal changes that promote bacterial internalization. These potentially cytotoxic alterations are rapidly reversed by the effector SptP, a tyrosine phosphatase and GTPase activating protein (GAP) that targets Cdc42 and Rac1. The 2.3 A resolution crystal structure of an SptP-Rac1 transition state complex reveals an unusual GAP architecture that mimics host functional homologs. The phosphatase domain possesses a conserved active site but distinct surface properties. Binding to Rac1 induces a dramatic stabilization in SptP of a four-helix bundle that makes extensive contacts with the Switch I and Switch II regions of the GTPase.

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