Identification of an amino-terminal substrate-binding domain in the Yersinia tyrosine phosphatase that is required for efficient recognition of focal adhesion targets.

YopH is a protein tyrosine phosphatase (PTP) that is delivered into host mammalian cells via a type III secretion pathway in pathogenic Yersinia species. Although YopH is a highly active PTP, it preferentially targets a subset of tyrosine-phosphorylated proteins in host cells, including p130Cas. Previous in vitro studies have indicated that the carboxy-terminal PTP domain contributes specificity to the interaction of YopH with substrates. However, it is not known if the PTP domain is sufficient for substrate recognition by YopH. Here, we have identified paxillin as an additional substrate of YopH in HeLa cells. In addition, we have identified a domain in the amino-terminal region of YopH that binds to both p130Cas and paxillin and is required for the efficient recognition of substrates by the wild-type enzyme. This 'substrate-binding' domain exhibits a ligand specificity that is similar to that of the Crk Src homology 2 (SH2) domain, and it binds substrates directly in a phosphotyrosine-dependent manner. The substrate-binding domain of YopH may represent a novel type of protein-protein interaction module, as it lacks significant sequence similarity with any known SH2 or phosphotyrosine-binding (PTB) domain.