High-throughput characterization of lipopolysaccharide-binding proteins using mass spectrometry.

Lipopolysaccharide (LPS)-binding proteins interact with LPS in human serum and mediate various immune responses. We describe a high-throughput LPS-binding protein profiling platform for discovering unknown LPS-binding proteins and potential inflammatory mediators. As a pull-down method, the LPS molecules were immobilized onto epoxy beads and then directly incubated with human serum to screen LPS-binding proteins. Through the "untargeted" mass spectrometric approach, potential LPS-binding proteins which elicit various immune responses in human serum were identified by a highly sensitive LTQ Orbitrap Hybrid Fourier Transform Mass Spectrometer (LTQ Orbitrap FT MS). Therefore, this mass spectrometry (MS)-based profiling method is straightforward for screening unknown LPS-binding proteins and provides physiologically relevant binding partners in human serum.