Purification of the S. Typhimurium TLR11 Ligand
S. Typhimurium (SL1344) was grown overnight at 37°C without shaking, collected by centrifugation, washed once in 10 mM Tris (pH 8), and homogenized in a Warring Blender for 5 × 10 s followed by heating at 60°C for 30 min. The resulting product was centrifuged at 10,000 ×g for 30 min, and the supernatant was ultracentrifuged at 100,000 ×g for 60 min. The resulting supernatant was treated with polymyxin B (Thermo/Pierce), applied to a DEAE Sephacel column, and eluted by step elution with 250 and 500 mM NaCl. Dialyzed fractions were assessed by NF-κB luciferase reporter assay, and fractions of interest were pooled and subjected to CM Sepharose chromatography. Fractions containing peak activity (flow through) were applied to Mono Q column and eluted with a linear 50–500 mM NaCl gradient (AKTA, GE biosciences). Fractions containing stimulatory activity were resolved by SDS-PAGE and visualized by Coomassie. A single band coeluting with the TLR11 stimulatory activity was excised and subjected to in-gel tryptic digest and MS analysis (Columbia University Protein Core Facility).