Lipid–protein interactions in the membrane: Studies with model peptides

Abstract

We have used fluorescence quenching of tryptophan-containing trans-membrane peptides by bromine-containing phospholipids to study the specificity of peptide–lipid interactions. We have synthesized peptides Ac-K₂GL_mWL_nK₂A-amide where m=7 and n=9 (L₁₆) and m=10 and n=12 (L₂₂). Binding constants of L₂₂ for dioleoylphosphatidylserine [di(C18:1)PS] or dioleoylphosphatidic acid [di(C18:1)PA] relative to dieoleoylphosphatidylcholine [di(C18:1)PC] were close to 1. However, for L₁₆, whilst the bulk of the di(C18:1)PA molecules bound with a binding constant relative to di(C18:1)PC close to 1, a small number of di(C18:1)PA molecules bound much more strongly. Assuming just one high affinity binding site on L₁₆ for anionic lipid, the affinity of the site for di(C18:1)PS was calculated to be ca. 8 times that for di(C18:1)PC. The relative binding constant was little affected by ionic strength and close contact between the anionic headgroup of di(C18:1)PS and a lysine residue on the peptide was suggested. The relative binding constant for di(C18:1)PS at this high affinity site was less than for di(C18:1)PA. Cholesterol interacts with L₂₂ with an affinity about 0.7 of that of di(C18:1)PC. The structure of the peptide itself is important. The peptide Ac-KKGYL₆WL₈YKKA-amide (Y₂L₁₄) incorporated into bilayers of dinervonylphosphatidylcholine [di(C24:1)PC] whereas L₁₆ did not incorporate into this lipid. It is suggested that thinning of a lipid bilayer around a peptide to give optimal hydrophobic matching is less energetically unfavourable when a Tyr residue is located in the lipid/water interfacial region.

References

1. D. C. Rees, A. J. Chirino, K. H. Kim and H. Komiya, in Membrane Protein Structure, ed. S. H. White, OUP, New York, 1994, p. 3.
2. A. G. Lee, K. A. Dalton, R. C. Duggleby, J. M. East and A. P. Starling, Biosci. Rep., 1995, 15, 289.
3. A. G. Lee, Biochim. Biophys. Acta, 1998, 1376, 381.
4. F. Michelangeli, E. A. Grimes, J. M. East and A. G. Lee, Biochemistry, 1991, 30, 342.
5. A. P. Starling, J. M. East and A. G. Lee, Biochem. J., 1995, 310, 875.
6. A. P. Starling, J. M. East and A. G. Lee, Biochemistry, 1995, 34, 3084.
7. A. P. Starling, K. A. Dalton, J. M. East, S. Oliver and A. G. Lee, Biochem. J., 1996, 320, 309.
8. K. A. Dalton, J. M. East, S. Mall, S. Oliver, A. P. Starling and A. G. Lee, Biochem. J., 1998, 329, 637.
9. C. J. Brandl, N. M. Green, B. Korczak and D. H. MacLennan, Cell, 1986, 44, 597.
10. A. G. Lee, in Biomembranes, Volume 5. The AT Pases., ed. A. G. Lee, JAI Press, Greenwich, Connecticut, 1996, p. 1.
11. R. J. Webb, J. M. East, R. P. Sharma and A. G. Lee, Biochemistry, 1998, 37, 673.
12. J. C. Huschilt, B. M. Millman and J. H. Davis, Biochim. Biophys. Acta, 1989, 979, 139.
13. F. A. Nezil and M. Bloom, Biophys. J., 1992, 61, 1176.
14. J. M. East and A. G. Lee, Biochemistry, 1982, 21, 4144.
15. A. C. Simmonds, J. M. East, O. T. Jones, E. K. Rooney, J. McWhirter and A. G. Lee, Biochim. Biophys. Acta, 1982, 693, 398.
16. E. Atherton and R. C. Sheppard, Solid phase peptide synthesis: a practical approach, IRL Press, Oxford, 1989.
17. J. M. East, D. Melville and A. G. Lee, Biochemistry, 1985, 24, 2615.
18. E. London and G. W. Feigenson, Biochemistry, 1981, 20, 1932.
19. J. R. Lakowicz, Principles of Fluorescence Spectroscopy, Plenum Press, New York, 1983.
20. B. A. Lewis and D. M. Engelman, J. Mol. Biol., 1983, 166, 211.
21. Y. P. Zhang, R. N. A. H. Lewis, R. S. Hodges and R. N. McElhaney, Biochemistry, 1992, 31, 11579.
22. Y. P. Zhang, R. N. A. H. Lewis, R. S. Hodges and R. N. McElhaney, Biophys. J., 1995, 68, 847.
23. G. Cevc, Biochim. Biophys. Acta, 1990, 1031, 311.
24. T. B. Woolf, Biophys. J., 1998, 74, 115.
25. M. Esmann and D. Marsh, Biochemistry, 1985, 24, 3572.
26. S. Iwata, C. Ostermeier, B. Ludwig and H. Michel, Nature, 1995, 376, 660.
27. J. Ding, A. P. Starling, J. M. East and A. G. Lee, Biochemistry, 1994, 33, 4974.