CONICET | Buscador de Institutos y Recursos Humanos

The Pfam PF04536 TPM_phosphatase family is a broadly conserved family ofdomains found across prokaryotes, plants and invertebrates. Despite having asimilar protein fold, members of this family have been implicated in diversecellular processes and found in varied subcellular localizations. Veryrecently, the biochemical characterization of two evolutionary divergent TPMdomains has shown that they are able to hydrolyze phosphate groups fromdifferent substrates. However, there are still incorrect functional annotationsand uncertain relationships between the structure and function of this familyof domains. BA41 is an uncharacterized single-pass transmembrane protein fromthe Antarctic psychrotolerant bacterium Bizionia argentinensis with a predictedcompact extracytoplasmic TPM domain and a C terminal cytoplasmic low complexityregion. To shed light on the structural properties that enable TPM domains toadopt divergent roles, we here accomplish a comprehensive structural andfunctional characterization of the central TPM domain of BA41 (BA41-TPM).Contrary to its predicted function as a beta-propeller methanol dehydrogenase,light scattering and crystallographic studies showed that BA41-TPM behaves as aglobular monomeric protein and adopts a conserved Rossmann fold, typically observedin other TPM domain structures. Although the crystal structure reveals theconservation of residues involved in substrate binding, no putative catalyticor intramolecular metal ions were detected. Most important, however, extensive biochemical studies demonstrated thatBA41-TPM has hydrolase activity against ADP, ATP, and other di- and triphosphatenucleotides and shares properties of coldadapted enzymes. The role of BA41 inextracellular ATP-mediated signaling pathways and its occurrence inenvironmental and pathogenic microorganisms is discussed.

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