Effector proteins function to alter host cell physiology and promote bacterial survival in host tissues. This protein includes tyrosine phosphatase and GTPase activating protein (GAP) activities. After bacterial internalization, GAP mediates the reversal of the cytoskeletal changes induced by SopE. This function is independent of its tyrosine phosphatase activity, which remains unclear. H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate The tyrosine phosphatase activity is inhibited by sodium vanadate. Forms a complex with SicP. Binds host RAC1. Secreted via type III secretion system 1 (SPI-1 TTSS), and delivered into the host cytoplasm. Requires SicP as a chaperone for its stability and for secretion. The structure of the SptP-SicP complex contains four molecules of the chaperone SicP, aligned in a linear fashion and arranged in two sets of tightly bound homodimers that bind two SptP molecules. The SicP homodimers do not interact with each other, but are held together by a molecular interface formed between two SptP molecules. The chaperone-binding domain of SptP does not adopt a globular fold for interaction with SicP. Each SptP molecule is wrapped around by three SicP chaperones (two chaperones from one homodimer and a third one from the opposite homodimer pair). SptP interacts with SicP chaperone dimers mainly through four regions of its chaperone-binding domain. In the N-terminal section; belongs to the YopE family.