1 / 23

Protein-membrane association.

This study explores the theoretical model of protein-membrane associations, employing the Lekner summation technique to accurately compute electrostatic interactions between proteins and lipid membranes. Given the crucial roles these interactions play in biological functions, we discuss the dynamics of integral and peripheral membrane proteins, the thermodynamics of binding free energy, and changes in conformational states. Insights gained from modeling these interactions pave the way for improved understanding of protein behavior at membrane interfaces and can guide future protein-relevant research.

veta
Télécharger la présentation

Protein-membrane association.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Protein-membrane association. Theoretical model, Lekner summation A.H. Juffer The University of Oulu Finland-Suomi A.H.Juffer The University of Oulu Finland-Suomi A.H.Juffer The University of Oulu Finland-Suomi A.H.Juffer The University of Oulu Finland-Suomi A.H.Juffer The University of Oulu Finland-Suomi A.H.Juffer The University of Oulu Finland-Suomi

  2. Previous work • W. Xin and A.H. Juffer, Polarization and dehydration effects in protein-membrane association, To Be Submitted, 2004 • W.Xin and A.H. Juffer, A BEM formulation of biomolecular interaction, To Be Submitted, 2004 • C.M. Shepherd, H.J. Vogel and A.H. Juffer, Monte Carlo and molecular dynamics studies of peptide-bilayer binding, in: High Performance Computing Systems and Applications 2000 (Nikitas J. Dimpoulos and Kin F. Li, Eds.), Kluwer Academic Publishers (Dordrechts, The Netherlands), Chapter 29, 447-464, 2002. • C.M. Shepherd, K.A. Schaus, H.J. Vogel and A.H. Juffer, A Molecular Dynamics Study of Peptide-Bilayer Adsorption. Biophys. J. 80, 579-596, 2001. • A.H. Juffer, C.M. Shepherd and H.J. Vogel, Protein-membrane electrostatic interactions: Application of the Lekner summation technique. J. Chem. Phys. 114, 1892-1905, 2001. • A.H. Juffer, J. de Vlieg and P. Argos, Adsorption of Proteins onto Charged Surfaces: A Monte Carlo Approach with Explicit Ions. J. Comput. Chem., 17, 1783-1803, 1996.

  3. Background • Interactions between lipid molecules and proteins crucial role in regulation biological function. • Membrane proteins: • Integral proteins: e.g. photosynthetic reaction center: • Fully embedded into membrane • Peripheral proteins: e.g. phospholipase C-1: • Only weakly bound to surface, separable by change in pH or ionic strength

  4. Background • Understanding the physics of protein-lipid interactions leads to deeper insight Equilibrium constant ↕ Standard free energy THERMODYNAMICS, NOT MECHANISM

  5. Modeling protein-membrane binding lipid bilayers sandostatin

  6. Free energy of binding Conformational Change. Non-polar hydrophobic effect (expulsion of non-polar compounds from water Changes in motional degrees of freedom. Difference in dielectric properties between water and hydrocarbon region (mutual polarization effects). Direct electrostatic interaction between basic residues and anionic lipids. Changes inside membrane.

  7. Coulomb interaction rij + + Long-ranged: beyond dimension of protein

  8. How to calculate it? Assume periodicity along x, y-direction Lx Ly q Image Ly

  9. The Lekner Summation Conditionally converging sum Fast absolutely converging sum

  10. Four surface charges: potential

  11. Four surface charges: field

  12. Ions next to flat surface • carrying a negative surface • charge density. • Accumulation of Na+. • Depletion of Cl-. • Electric moment pointing • towards flat surface. • Symmetry along x- and y-axis • but not along z-axis. z-axis

  13. Ion densities near POPC

  14. Ion densities near POPG

  15. Free energy of adsorption Change in free energy in moving protein from bulk solution at z=- to A point z=z0 near the surface: Thermodynamic integration

  16. Electrostatic force acting on Sandostatin POPC

  17. Force acting on Sandostatin, MD POPC

  18. Movie The first 2 ns of a 6 ns MD simulation. Biophys. J. 80, 579-596, 2001.

  19. Electrostatic force acting on Sandostatin POPG

  20. Two solutes A, B immersed in polarizable solvent S Q Solvent cavity q B A approximation

  21. Two polarisable objects

  22. Future improvements • Inclusion of internal (`essential’) degrees of freedom. • Dynamical simulations • Stochastic modeling of proteins • Effects of pH.

  23. Weidong Xin Craig Shepherd Heritage Foundation Human frontiers MRC Biocenter Academy of Finland. Acknowledgements

More Related