[Bioinformatics, expression, purification, and inflammation-inducing effect of Mycoplasma genitalium GroEL protein]

To preliminarily understand the pathogenic mechanism of Mycoplasma genitalium (Mg) GroEL protein, we used bioinformatics tools to predict the structure and function of Mg GroEL protein and then constructed the recombinant plasmid pET-28a-GroEL. The protein expression was induced by 0.2 mmol/L IPTG, and the expressed protein was purified by Ni-iminodicitic acid (IDA) column affinity. Tohoku Hospital Pediatrics-1 (THP-1) cells were exposed to 2 μg/mL Mg rGroEL. The levels of interleukin (IL)-1β and tumor necrosis factor (TNF)-α in the cell supernatant were measured by ELISA, and that of IL-6 was measured by an automatic chemiluminescence instrument. The activation of the nuclear factor-kappa B (NF-κB) signaling pathway was visualized by immunofluorescence and Western blotting. The results showed that Mg GroEL was a stable hydrophilic protein composed of 543 amino acid residues, with the relative molecular mass of 58.44 kDa, an isoelectric point of 5.68, and a molecular formula of C₂₅₆₈H₄₃₀₀N₇₀₀O₈₂₅S₈. The secondary structure was mainly composed of α-helices and random coils. Mg GroEL contained 12 B-cell dominant epitopes and 10 T-cell dominant epitopes. It exhibited high homology with the GroEL proteins from Mycoplasma pneumoniae, M. agalactiae, M. arthritidis, M. hyopneumoniae, and M. bovis. Mg rGroEL activated the NF-κB signaling pathway and promoted the secretion of IL-1β, IL-6, and TNF-α in THP-1 cells. These results suggest that Mg GroEL exhibits substantial antigenicity and possesses the capability of triggering inflammation in host cells. This study establishes a theoretical basis for future investigations pertaining to the role and pathogenic mechanisms of Mg GroEL.