Dual specificity phosphatases (DUSPs) are a subfamily of protein tyrosine phosphatases that regulate diverse cellular processes through dephosphorylation of phosphorylated substrates. DUSPs are commonly found in eukaryotes, bacteria, archaea, and viruses. However, structural and biochemical characterization of bacterial DUSP remains limited, as only one bacterial DUSP has been identified thus far. In this study, we investigated a novel putative bacterial DUSP from Candidatus Chlorohelix allophototropha, referred to as CCaDUSP. The crystal structure of CCaDUSP showed the presence of a well-conserved catalytic motif with a characteristic phosphate-binding loop. Biochemical analyses further confirmed that CCaDUSP exhibits phosphatase activity and contains dual general acid/base residues, both of which contribute to its enzymatic activity. These findings not only represent the first characterization of a novel bacterial DUSP with dual general acid/base residues but also provide a foundation for understanding the diversity of DUSP proteins in bacteria.

Dual specificity phosphatases (DUSPs), a subfamily of the protein tyrosine phosphatase (PTP) family, dephosphorylate not only phosphotyrosine but also phosphoserine and phosphothreonine residues. Beyond the 26 members of this family in humans, DUSPs represent the only type of PTPs found across a wide range of microorganisms, including bacteria, archaea, and viruses. This review presents a comprehensive structural analysis of human and microbial DUSPs. These proteins commonly share core features, such as a typical DUSP fold, shallow active site pocket, signature active site motif known as the P-loop, and conserved aspartate residue that acts as a general acid/base. However, DUSPs from diverse microorganisms also display unique structural and functional characteristics. Pseudomonas aeruginosa TpbA is the only bacterial DUSP identified to date, while a second candidate was proposed in this review. Archaeal DUSPs are hyperthermostable, contain a unique motif in their P-loops, and employ dual general acid/base residues. Poxviral DUSPs are characterized by the formation of domain-swapped homodimers. The presence of DUSPs across all domains of life and viruses, along with their low specificity for phosphorylated amino acids and structural similarity to classical PTPs, suggests that DUSPs represent the ancestral form of PTPs.