Protein tyrosine phosphatase, non-receptor type 1 Adenovirus (Ad-PTP1B)

Protein phosphatases play critical roles in the regulation of signal transduction pathways. The family can be separated into three general categories, which are distinguished on the basis of substrate specificity. The first and largest category, termed protein tyrosine phosphatases or PTPs, includes transmembrane proteins, membrane associated proteins and proteins that localize to nuclei. Transmembrane PTPs, such as PTP precursors alpha, beta, gamma, epsilon, LAR, HePTP, RPTP-alpha, PTPRN2 and CD45 are involved in homophilic binding and facilitate cell-cell communication. Membrane associated PTPs include the following proteins SH-PTP1 (PTP1C, HCP, SHP), SH-PTP2 (Syp, PTP1D), PTP-H1 and PTP1B. Fap-1 (also designated PTP-BAS) contains an ezrin-like membrane binding domain and through its association with FAS presumably regulates FAS signaling. PTPs, such as KAP (also designated Cdi1), function to regulate the activity of proteins in the nuclei of cells. The second category of protein phosphatases dephosphorylate proteins on phosphoserine and phosphothreonine residues, whereas the third category of protein phosphatases exhibit dual specificities and can dephosphorylate proteins on phosphotyrosine and phosphoserine/phosphothreonine residues.