Crystal structure of the PSPTO-PSP protein from Pseudomonas syringae pv. tomato str. DC3000 in complex with d-glucose

The perchloric acid-soluble protein (PSP) is an endoribonuclease and on the basis of sequence similarity has been assigned to the YjgF/YER057c/UK114 family. These family members are ubiquitous and highly conserved in evolution, and participate in regulating basic cellular metabolism. Here we present the 2.1 Å crystal structure of the PSP protein from Pseudomonas syringae pv. tomato str. DC3000 (PSPTO-PSP), in complex with d-glucose. The quaternary structure of PSPTO-PSP is a homologous trimer. Glucose is located in the cavity between each two monomers. Comparison of the hydrogen bonds between ligands and YjgF/YER057c/UK114 family homologues confirms that the conserved Arg103 of PSPTO-PSP is a key amino acid in this cavity for ligand binding. It indicated that the involvement of PSPTO-PSP in essential cellular mechanism was regulated by glucose occupying this active site.