InterPro domain: IPR030675

This entry represents the bactericidal permeability-increasing protein (BPI) and the lipopolysaccharide-binding protein (LBP). The crystal structures of BPI and LBP are similar [ 1 ], and they may represent a common gene family of lipid-binding proteins [ 2 ].

In mammals, LBP and BPI mediate the biological effects of LPS (lipopolysaccharide), a glycolipid present in the outer membrane of Gram-negative bacteria. LBP is a plasma protein that enhances the inflammatory response to LPS, whereas BPI is found in lysosomal granules of polymorphonuclear neutrophils, is bactericidal, and neutralises the toxic effects of LPS [ 3 , 4 ].

LBP is an acute phase serum protein secreted mainly by the liver that modulates the LPS-induced immune response. LBP binds mainly to the lipid A moiety of LPS and acts as an affinity enhancer for CD14, facilitating its association with LPS [ 5 ].

1. Crystal structure of human BPI and two bound phospholipids at 2.4 angstrom resolution. Science 276, 1861-4
2. Similar organization of the lipopolysaccharide-binding protein (LBP) and phospholipid transfer protein (PLTP) genes suggests a common gene family of lipid-binding proteins. Genomics 46, 416-25
3. Prospects for use of recombinant BPI in the treatment of gram-negative bacterial infections. Infect Agents Dis 4, 102-9
4. Bactericidal/permeability-increasing protein and lipopolysaccharide (LPS)-binding protein. LPS binding properties and effects on LPS-mediated cell activation. J. Biol. Chem. 269, 17411-6
5. Lipopolysaccharide binding protein participation in cellular activation by LPS. Crit. Rev. Immunol. 15, 201-14