A Multilayered Approach to Predict Metal-Binding Sites in the Pneumococcal Phosphoglucomutase Protein

Phosphoglucomutase (Pgm) is an important enzyme that functions to bridge sugar metabolism to capsular polysaccharide formation in Streptococcus pneumoniae. Preliminary data using a mag-fura-2 metal-binding competition assay reveals that pneumococcal Pgm binds 2 metal ions per protomer, despite literature showing a single metal-binding site for other characterized Pgm family members. In this study, we focus on identifying the second metal-binding site in the pneumococcal Pgm. I-TASSER was used to generate a structural model of the pneumococcal Pgm. A multi-protein sequence alignment comparing pneumococcal Pgm and other bacterial Pgm proteins using multiple bioinformatics programs validated the known highly conserved metal-binding motif DXDXDR, as well as several other potential metal-binding motifs. We share information here on two of these secondary predicted metal-binding motifs. One motif is found downstream of the Pgm active site and the other is located near the C-terminus of the protein. These preliminary data set the foundation for further biochemical and phenotypical analysis of mutant Pgm protein.