The active core of the dual specificity protein phosphatase is made up of two globular domains both with the DSP-like fold. This family represents the N-terminal half of the core. These domains are arranged in tandem, and are associated via an extensive interface to form a single globular whole. The conserved PTP signature motif (Cys-[X]5-Arg) that defines the catalytic centre of all PTP-family members is located within the C-terminal domain, family DSPc, Pfam:PF00782. Although the centre of the catalytic site is formed from DSPc, two loops from the N-terminal domain, DSPn, also contribute to the catalytic site, facilitating peptide substrate specificity [1].

1: The structure of the cell cycle protein Cdc14 reveals a proline-directed protein phosphatase. Gray CH, Good VM, Tonks NK, Barford D; EMBO J. 2003;22:3524-3535. PMID:12853468