TYROSINE PHOSPHATASE SHP-2
[PTN11_HUMAN] Defects in PTPN11 are the cause of LEOPARD syndrome type 1 (LEOPARD1) [MIM:151100]. It is an autosomal dominant disorder allelic with Noonan syndrome. The acronym LEOPARD stands for lentigines, electrocardiographic conduction abnormalities, ocular hypertelorism, pulmonic stenosis, abnormalities of genitalia, retardation of growth, and deafness.       Defects in PTPN11 are the cause of Noonan syndrome type 1 (NS1) [MIM:163950]. Noonan syndrome (NS) is a disorder characterized by dysmorphic facial features, short stature, hypertelorism, cardiac anomalies, deafness, motor delay, and a bleeding diathesis. Some patients with Noonan syndrome type 1 develop multiple giant cell lesions of the jaw or other bony or soft tissues, which are classified as pigmented villomoduolar synovitis (PVNS) when occurring in the jaw or joints. Note=Mutations in PTPN11 account for more than 50% of the cases. Rarely, NS is associated with juvenile myelomonocytic leukemia (JMML). NS1 inheritance is autosomal dominant.            Defects in PTPN11 are a cause of juvenile myelomonocytic leukemia (JMML) [MIM:607785]. JMML is a pediatric myelodysplastic syndrome that constitutes approximately 30% of childhood cases of myelodysplastic syndrome (MDS) and 2% of leukemia. It is characterized by leukocytosis with tissue infiltration and in vitro hypersensitivity of myeloid progenitors to granulocyte-macrophage colony stimulating factor. Defects in PTPN11 are a cause of metachondromatosis (MC) [MIM:156250]. It is a skeletal disorder with radiologic fetarures of both multiple exostoses and Ollier disease, characterized by the presence of multiple enchondromas and osteochondroma-like lesions.
[PTN11_HUMAN] Acts downstream of various receptor and cytoplasmic protein tyrosine kinases to participate in the signal transduction from the cell surface to the nucleus. Dephosphorylates ROCK2 at Tyr-722 resulting in stimulatation of its RhoA binding activity.  
Publication Abstract from PubMed
The structure of the SHP-2 tyrosine phosphatase, determined at 2.0 angstroms resolution, shows how its catalytic activity is regulated by its two SH2 domains. In the absence of a tyrosine-phosphorylated binding partner, the N-terminal SH2 domain binds the phosphatase domain and directly blocks its active site. This interaction alters the structure of the N-SH2 domain, disrupting its phosphopeptide-binding cleft. Conversely, interaction of the N-SH2 domain with phosphopeptide disrupts its phosphatase recognition surface. Thus, the N-SH2 domain is a conformational switch; it either binds and inhibits the phosphatase, or it binds phosphoproteins and activates the enzyme. Recognition of bisphosphorylated ligands by the tandem SH2 domains is an integral element of this switch; the C-terminal SH2 domain contributes binding energy and specificity, but it does not have a direct role in activation.
Crystal structure of the tyrosine phosphatase SHP-2.,Hof P, Pluskey S, Dhe-Paganon S, Eck MJ, Shoelson SE Cell. 1998 Feb 20;92(4):441-50. PMID:9491886
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.