Role of the cyclosporin-A-cyclophilin complex, FK506-FK506-binding protein complex and calcineurin in the inhibition of T-cell signal transduction: Current opinion in structural biology 1993, 3:929–933

SH2 and SH3 domains are small protein modules of about 100 and 60 amino acids, respectively, that are found in many proteins involved in intracellular signal transduction. SH2 and SH3 domains mediate protein-protein interactions and modulate enzyme activity by their ability to bind to specific phosphorylated tyrosine residues or proline-rich sequences, respectively. The recent determination of the three-dimensional structures of several SH2 and SH3 domains has led to considerable progress in understanding their mechanism of action, and these structures are the focus of this review.