Figure 1.

Identification of HMGB1 as a novel metformin-binding protein. A, structure of metformin (upper) and the biotinylated compound containing metformin-like biguanide structure (lower) used for the affinity chromatography. B, affinity purification was performed from rat liver cytosol with the metformin beads and the control biotin beads. Bead eluates were analyzed by SDS-PAGE followed by silver staining. Mass spectrometry analysis revealed the ∼25-kDa protein indicated by the arrow was HMGB1. C, HMGB1 in cytosolic fraction of HepG2 cells was pulled down with the metformin beads in the presence of indicated concentrations of metformin. D, recombinant HMGB1 was pulled down with the metformin beads or control beads in the presence of the indicated concentrations of metformin, phenformin, putrescine, or 6-aminohexanoic acid. Data shown are representative of three independent experiments with similar results.