Crystal structure of unphosphorylated Spo0F from Paenisporosarcina sp. TG-14, a psychrophilic bacterium isolated from an Antarctic glacier

Abstract

Spo0F is a response regulator that modulates sporulation, undergoes phosphorylation for phosphorelay signal transduction,and interacts with various regulatory proteins; however, the mechanisms through which phosphorylation induces structuralchanges and regulates interactions with binding partners remain unclear. Here, we determined the unphosphorylatedcrystal structure of Spo0F from the psychrophilic bacterium Paenisporosarcina sp. TG-14 (PaSpo0F) and establisheda phosphorylation-state structural model. We found that PaSpo0F underwent structural changes (Lys54 and Lys102)by phosphorylation and generated new interactions (Lys102/Gln10 and Lys54/Glu84) to stabilize the β4/α4 and β1/α1loop structures, which are important target-protein binding sites. Analysis of Bacillus subtilis Spo0 variants revealedmovement by BsSpo0F Thr82 and Tyr84 residues following interaction with BsSpo0B, providing insight into the movementof corresponding residues in PaSpo0F (Thr80 and Tyr82), with further analysis of BsSpo0F/BsRapH interaction revealingalterations in the β4/α4 loop region. These results suggest that phosphorylation-induced structural rearrangement mightbe essential for PaSpo0F activation and expand the understanding of Spo0F-specific activation mechanisms duringsporulation.