Fructose 1,6-bisphosphate aldolase (FBA) is important for both glycolysis and gluconeogenesis in life. Class II (zinc dependent) FBA is an attractive target for the development of antibiotics against protozoa, bacteria, and fungi, and is also widely used to produce various high-value stereoisomers in the chemical and pharmaceutical industry. In this study, the crystal structures of class II Escherichia coli FBA (EcFBA) were determined from four different crystals, with resolutions between 1.8 Å and 2.0 Å. Native EcFBA structures showed two separate sites of Zn1 (interior position) and Zn2 (active site surface position) for Zn2+ ion. Citrate and TRIS bound EcFBA structures showed Zn2+ position exclusively at Zn2. Crystallographic snapshots of EcFBA structures with and without ligand binding proposed the rationale of metal shift at the active site, which might be a hidden mechanism to keep the trace metal cofactor Zn2+ within EcFBA without losing it.
Xanthomonas oryzae pv. oryzae (Xoo) is a plant pathogen that causes bacterial blight of rice, with outbreaks occurring in most rice-growing countries. Thus far, there is no effective pesticide against bacterial blight. Chaperones in bacterial pathogens are important for the stabilization and delivery of effectors into host cells to cause disease. In bacteria, GroEL/GroES complex mediates protein folding and protects proteins against misfolding and aggregation caused by environmental stress. We determined the crystal structure of GroEL from Xanthomonas oryzae pv. oryzae (XoGroEL) at 3.2 Å resolution, which showed the open form of two conserved homoheptameric rings stacked back-to-back. In the open form structure, the apical domain of XoGroEL had a higher B factor than the intermediate and equatorial domains, indicating that the apical domain had a flexible conformation before the binding of substrate unfolded protein and ATP. The XoGroEL structure will be helpful in understanding the function and catalytic mechanism of bacterial chaperonin GroELs.
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