The phosphotyrosine-binding domain (PTB, also phosphotyrosine-interaction or PI domain) in the protein tensin tends to be found at the C-terminus. Tensin is a multi-domain protein that binds to actin filaments and functions as a focal-adhesion molecule (focal adhesions are regions of plasma membrane through which cells attach to the extracellular matrix). Human tensin has actin-binding sites, an SH2 (Pfam:PF00017) domain and a region similar to the tumour suppressor PTEN [1]. The PTB domain interacts with the cytoplasmic tails of beta integrin by binding to an NPXY motif [2].

1: Molecular characterization of human tensin. Chen H, Ishii A, Wong WK, Chen LB, Lo SH; Biochem J 2000;351:403-411. PMID:11023826

2: Tensin. Lo SH; Int J Biochem Cell Biol 2004;36:31-34. PMID:14592531