The structure of bradyzoite-specific enolase from Toxoplasma gondii reveals insights into its dual cytoplasmic and nuclear functions

• Published in: Acta crystallographica. Section D, Biological crystallography. Biological crystallography., 2015-03, Vol.71 (Pt 3)
• Main Authors: Ruan, Jiapeng, Mouveaux, Thomas, Light, Samuel H., Minasov, George, Anderson, Wayne F., Tomavo, Stanislas, Ngô, Huân M., BrainMicro LLC, 21 Pendleton Street, New Haven, CT 06511
• Format: Article
• Language: English
• Subjects: CAPTURE; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRYSTAL STRUCTURE; CRYSTALS; DESIGN; DNA; GELS; IN VIVO; INTERACTIONS; MATRICES; PLASMA; POTENTIALS; RESOLUTION; SURFACES
• ISSN: 0907-4449; 1399-0047

The second crystal structure of a parasite protein preferentially enriched in the brain cyst of T. gondii has been solved at 2.75 Å resolution. Bradyzoite enolase 1 is reported to have differential functions as a glycolytic enzyme and a transcriptional regulator in bradyzoites. In addition to catalyzing a central step in glycolysis, enolase assumes a remarkably diverse set of secondary functions in different organisms, including transcription regulation as documented for the oncogene c-Myc promoter-binding protein 1. The apicomplexan parasite Toxoplasma gondii differentially expresses two nuclear-localized, plant-like enolases: enolase 1 (TgENO1) in the latent bradyzoite cyst stage and enolase 2 (TgENO2) in the rapidly replicative tachyzoite stage. A 2.75 Å resolution crystal structure of bradyzoite enolase 1, the second structure to be reported of a bradyzoite-specific protein in Toxoplasma, captures an open conformational state and reveals that distinctive plant-like insertions are located on surface loops. The enolase 1 structure reveals that a unique residue, Glu164, in catalytic loop 2 may account for the lower activity of this cyst-stage isozyme. Recombinant TgENO1 specifically binds to a TTTTCT DNA motif present in the cyst matrix antigen 1 (TgMAG1) gene promoter as demonstrated by gel retardation. Furthermore, direct physical interactions of both nuclear TgENO1 and TgENO2 with the TgMAG1 gene promoter are demonstrated in vivo using chromatin immunoprecipitation (ChIP) assays. Structural and biochemical studies reveal that T. gondii enolase functions are multifaceted, including the coordination of gene regulation in parasitic stage development. Enolase 1 provides a potential lead in the design of drugs against Toxoplasma brain cysts.