The BPI/LBP family of proteins: a structural analysis of conserved regions (original) (raw)

Abstract

Two related mammalian proteins, bactericidal/permeability-increasing protein (BPI) and lipopolysaccharide-binding protein (LBP), share high-affinity binding to lipopolysaccharide (LPS), a glycolipid found in the outer membrane of gram-negative bacteria. The recently determined crystal structure of human BPI permits a structure/function analysis, presented here, of the conserved regions of these two proteins sequences. In the seven known sequences of BPI and LBP, 102 residues are completely conserved and may be classified in terms of location, side-chain chemistry, and interactions with other residues. We find that the most highly conserved regions lie at the interfaces between the tertiary structural elements that help create two apolar lipid-binding pockets. Most of the conserved polar and charged residues appear to be involved in inter-residue interactions such as H-bonding. However, in both BPI and LBP a subset of conserved residues with positive charge (lysines 42, 48, 92, 95, and 99 of BPI) have no apparent structural role. These residues cluster at the tip of the NH2-terminal domain, and several coincide with residues known to affect LPS binding; thus, it seems likely that these residues make electrostatic interactions with negatively charged groups of LPS. Overall differences in charge and electrostatic potential between BPI and LBP suggest that BPI's bactericidal activity is related to the high positive charge of its NH2-terminal domain. A model of human LBP derived from the BPI structure provides a rational basis for future experiments, such as site-directed mutagenesis and inhibitor design.

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Selected References

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  1. Abrahamson S. L., Wu H. M., Williams R. E., Der K., Ottah N., Little R., Gazzano-Santoro H., Theofan G., Bauer R., Leigh S. Biochemical characterization of recombinant fusions of lipopolysaccharide binding protein and bactericidal/permeability-increasing protein. Implications in biological activity. J Biol Chem. 1997 Jan 24;272(4):2149–2155. doi: 10.1074/jbc.272.4.2149. [DOI] [PubMed] [Google Scholar]
  2. Beamer L. J., Carroll S. F., Eisenberg D. Crystal structure of human BPI and two bound phospholipids at 2.4 angstrom resolution. Science. 1997 Jun 20;276(5320):1861–1864. doi: 10.1126/science.276.5320.1861. [DOI] [PubMed] [Google Scholar]
  3. Bowie J. U., Lüthy R., Eisenberg D. A method to identify protein sequences that fold into a known three-dimensional structure. Science. 1991 Jul 12;253(5016):164–170. doi: 10.1126/science.1853201. [DOI] [PubMed] [Google Scholar]
  4. Camussi G., Montrucchio G., Dominioni L., Dionigi R. Septic shock--the unravelling of molecular mechanisms. Nephrol Dial Transplant. 1995 Oct;10(10):1808–1813. [PubMed] [Google Scholar]
  5. Colovos C., Yeates T. O. Verification of protein structures: patterns of nonbonded atomic interactions. Protein Sci. 1993 Sep;2(9):1511–1519. doi: 10.1002/pro.5560020916. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Connolly M. L. Solvent-accessible surfaces of proteins and nucleic acids. Science. 1983 Aug 19;221(4612):709–713. doi: 10.1126/science.6879170. [DOI] [PubMed] [Google Scholar]
  7. Elsbach P., Weiss J., Kao L. The role of intramembrane Ca2+ in the hydrolysis of the phospholipids of Escherichia coli by Ca2+-dependent phospholipases. J Biol Chem. 1985 Feb 10;260(3):1618–1622. [PubMed] [Google Scholar]
  8. Elsbach P., Weiss J. Prospects for use of recombinant BPI in the treatment of gram-negative bacterial infections. Infect Agents Dis. 1995 Jun;4(2):102–109. [PubMed] [Google Scholar]
  9. Gazzano-Santoro H., Mészáros K., Birr C., Carroll S. F., Theofan G., Horwitz A. H., Lim E., Aberle S., Kasler H., Parent J. B. Competition between rBPI23, a recombinant fragment of bactericidal/permeability-increasing protein, and lipopolysaccharide (LPS)-binding protein for binding to LPS and gram-negative bacteria. Infect Immun. 1994 Apr;62(4):1185–1191. doi: 10.1128/iai.62.4.1185-1191.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Gazzano-Santoro H., Parent J. B., Grinna L., Horwitz A., Parsons T., Theofan G., Elsbach P., Weiss J., Conlon P. J. High-affinity binding of the bactericidal/permeability-increasing protein and a recombinant amino-terminal fragment to the lipid A region of lipopolysaccharide. Infect Immun. 1992 Nov;60(11):4754–4761. doi: 10.1128/iai.60.11.4754-4761.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Hailman E., Albers J. J., Wolfbauer G., Tu A. Y., Wright S. D. Neutralization and transfer of lipopolysaccharide by phospholipid transfer protein. J Biol Chem. 1996 May 24;271(21):12172–12178. doi: 10.1074/jbc.271.21.12172. [DOI] [PubMed] [Google Scholar]
  12. Han J., Mathison J. C., Ulevitch R. J., Tobias P. S. Lipopolysaccharide (LPS) binding protein, truncated at Ile-197, binds LPS but does not transfer LPS to CD14. J Biol Chem. 1994 Mar 18;269(11):8172–8175. [PubMed] [Google Scholar]
  13. Higgins D. G., Sharp P. M. CLUSTAL: a package for performing multiple sequence alignment on a microcomputer. Gene. 1988 Dec 15;73(1):237–244. doi: 10.1016/0378-1119(88)90330-7. [DOI] [PubMed] [Google Scholar]
  14. Horwitz A. H., Williams R. E., Nowakowski G. Human lipopolysaccharide-binding protein potentiates bactericidal activity of human bactericidal/permeability-increasing protein. Infect Immun. 1995 Feb;63(2):522–527. doi: 10.1128/iai.63.2.522-527.1995. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Iovine N. M., Elsbach P., Weiss J. An opsonic function of the neutrophil bactericidal/permeability-increasing protein depends on both its N- and C-terminal domains. Proc Natl Acad Sci U S A. 1997 Sep 30;94(20):10973–10978. doi: 10.1073/pnas.94.20.10973. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Lamping N., Hoess A., Yu B., Park T. C., Kirschning C. J., Pfeil D., Reuter D., Wright S. D., Herrmann F., Schumann R. R. Effects of site-directed mutagenesis of basic residues (Arg 94, Lys 95, Lys 99) of lipopolysaccharide (LPS)-binding protein on binding and transfer of LPS and subsequent immune cell activation. J Immunol. 1996 Nov 15;157(10):4648–4656. [PubMed] [Google Scholar]
  17. Little R. G., Kelner D. N., Lim E., Burke D. J., Conlon P. J. Functional domains of recombinant bactericidal/permeability increasing protein (rBPI23). J Biol Chem. 1994 Jan 21;269(3):1865–1872. [PubMed] [Google Scholar]
  18. Lüthy R., Bowie J. U., Eisenberg D. Assessment of protein models with three-dimensional profiles. Nature. 1992 Mar 5;356(6364):83–85. doi: 10.1038/356083a0. [DOI] [PubMed] [Google Scholar]
  19. Mannion B. A., Weiss J., Elsbach P. Separation of sublethal and lethal effects of the bactericidal/permeability increasing protein on Escherichia coli. J Clin Invest. 1990 Mar;85(3):853–860. doi: 10.1172/JCI114512. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Nicholls A., Sharp K. A., Honig B. Protein folding and association: insights from the interfacial and thermodynamic properties of hydrocarbons. Proteins. 1991;11(4):281–296. doi: 10.1002/prot.340110407. [DOI] [PubMed] [Google Scholar]
  21. Ooi C. E., Weiss J., Doerfler M. E., Elsbach P. Endotoxin-neutralizing properties of the 25 kD N-terminal fragment and a newly isolated 30 kD C-terminal fragment of the 55-60 kD bactericidal/permeability-increasing protein of human neutrophils. J Exp Med. 1991 Sep 1;174(3):649–655. doi: 10.1084/jem.174.3.649. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Pugin J., Schürer-Maly C. C., Leturcq D., Moriarty A., Ulevitch R. J., Tobias P. S. Lipopolysaccharide activation of human endothelial and epithelial cells is mediated by lipopolysaccharide-binding protein and soluble CD14. Proc Natl Acad Sci U S A. 1993 Apr 1;90(7):2744–2748. doi: 10.1073/pnas.90.7.2744. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Schromm A. B., Brandenburg K., Rietschel E. T., Flad H. D., Carroll S. F., Seydel U. Lipopolysaccharide-binding protein mediates CD14-independent intercalation of lipopolysaccharide into phospholipid membranes. FEBS Lett. 1996 Dec 16;399(3):267–271. doi: 10.1016/s0014-5793(96)01338-5. [DOI] [PubMed] [Google Scholar]
  24. Theofan G., Horwitz A. H., Williams R. E., Liu P. S., Chan I., Birr C., Carroll S. F., Mészáros K., Parent J. B., Kasler H. An amino-terminal fragment of human lipopolysaccharide-binding protein retains lipid A binding but not CD14-stimulatory activity. J Immunol. 1994 Apr 1;152(7):3623–3629. [PubMed] [Google Scholar]
  25. Tobias P. S., Soldau K., Iovine N. M., Elsbach P., Weiss J. Lipopolysaccharide (LPS)-binding proteins BPI and LBP form different types of complexes with LPS. J Biol Chem. 1997 Jul 25;272(30):18682–18685. doi: 10.1074/jbc.272.30.18682. [DOI] [PubMed] [Google Scholar]
  26. Weiss J., Victor M., Elsbach P. Role of charge and hydrophobic interactions in the action of the bactericidal/permeability-increasing protein of neutrophils on gram-negative bacteria. J Clin Invest. 1983 Mar;71(3):540–549. doi: 10.1172/JCI110798. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Wurfel M. M., Kunitake S. T., Lichenstein H., Kane J. P., Wright S. D. Lipopolysaccharide (LPS)-binding protein is carried on lipoproteins and acts as a cofactor in the neutralization of LPS. J Exp Med. 1994 Sep 1;180(3):1025–1035. doi: 10.1084/jem.180.3.1025. [DOI] [PMC free article] [PubMed] [Google Scholar]