In spite of the complications related to the CovID19 pandemic, our Structure-Based Drug Design (SBDD) group within the Institute of Tuberculosis Research (ITR) at UIC has continued to work on targets of interest related to M. tuberculosis.
These past few months have seen the complete biochemical characterization, structure determination and refinement of the Fructose,1-6-Bisphophatase of Francisella tularensis (FtFBPase), a very important pathogen, considered to be a significant bio-terrorism microorganism. This represents another milestone on the study of this important target (FBPases) for the survival of several pathogens in the host. Many of them need an effective way to synthesize glucose, and important related metabolites, inside the infected tissues of the patient, because the affected cells shutdown glucose availability and turn off glycolysis as a defense mechanism. Thus, an efficient gluconeogenic pathway is essential for survival and FBPases are the key regulated enzymes in that pathway.
Our work was complicated because, no matter how hard we tried, the crystals of the FtBPase enzyme always grew as imperfect, twinned, crystals that made it difficult to collect single-crystal, high quality, data. Nonetheless, we were able to collect data from a few crystals that allowed us to identify the twinning law and consequently correct the corresponding crystallographic data.
- The crystal structure revealed an approximate 222 (D2) tetramer (see Figure), very similar to the one we have seen in MtFBPase previously. The details of the structure in relation to the differences in the amino acid sequences with respect to MtFBPase and related FBPases (e.g. E. coli) was published recently in Acta Cryst F, Selezneva et al. (2020) 76, 524-536 (PubMed: 33135671 Search on PubMed DOI: 10.1107).PDB entry 7JS3. PDF
- We continue our work in other FBPases and we have recently completed the structure of the Staphilococcus aureus of great importance because of the widespread presence in the patient population of resistant strains (MER-Sa). SBDD projects focusing on these targets are on-going at ITR.