Abstract
BackgroundAntibacterial activity is a novel function of high-mobility group box 1 (HMGB1). However, the functional site for this new effect is presently unknown.Methods and ResultsIn this study, recombinant human HMGB1 A box and B box (rHMGB1 A box, rHMGB1 B box), recombinant human HMGB1 (rHMGB1) and the truncated C-terminal acidic tail mutant (tHMGB1) were prepared by the prokaryotic expression system. The C-terminal acidic tail (C peptide) was synthesized, which was composed of 30 amino acid residues. Antibacterial assays showed that both the full length rHMGB1 and the synthetic C peptide alone could efficiently inhibit bacteria proliferation, but rHMGB1 A box and B box, and tHMGB1 lacking the C-terminal acidic tail had no antibacterial function. These results suggest that C-terminal acidic tail is the key region for the antibacterial activity of HMGB1. Furthermore, we prepared eleven different deleted mutants lacking several amino acid residues in C-terminal acidic tail of HMGB1. Antibacterial assays of these mutants demonstrate that the amino acid residues 201-205 in C-terminal acidic tail region is the core functional site for the antibacterial activity of the molecule.ConclusionIn sum, these results define the key region and the crucial site in HMGB1 for its antibacterial function, which is helpful to illustrating the antibacterial mechanisms of HMGB1.
Highlights
Antibacterial activity is a novel function of high-mobility group box 1 (HMGB1)
We showed that the recombinant human HMGB1 and the synthetic C-terminal acidic tail (C peptide) presented antibacterial activity, the A box, B box domains of the molecule and the truncated HMGB1 lacking its C-terminal acidic tail failed to inhibit bacterial multiplication, which demonstrated that the C-terminal acidic tail is the key region for the antibacterial activity of HMGB1
Preparation of recombinant proteins Totally 16 recombinant proteins were prepared in this study, including recombinant human HMGB1 (rHMGB1), tHMGB1, rHMGB1 A box, rHMGB1 B box, eleven different deleted mutants lacking several amino acid residues in C-terminal acidic tail of HMGB1 and negative control protein DHFR
Summary
Antibacterial activity is a novel function of high-mobility group box 1 (HMGB1). High-mobility group box 1(HMGB1) belongs to highmobility group superfamily named for its characteristic rapid mobility in polyacrylamide gel electrophoresis (PAGE) [1]. It is highly conserved across species and wildly distribute in eukaryotic cells from yeast to human [2,3,4]. Human HMGB1 has 215 amino acid residues, including three main functional domains (A box, B box and a highly conservation, repetitive C terminus). HMGB1 is an endogenous nuclear protein that can be translocated to the cytoplasm and released extracellularly. Cytoplasmal and extracellular HMGB1 has been extensively related to the growth of neurite, malignant tumor metastasis, arthero-
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