How mechanical force regulates the function of proteins? Vesa Hytönen Research group of Professor Viola Vogel, Biologically Oriented Materials, Department of Materials, ETH- Hönggerberg, Zürich Beowulf Day January 30th, 2006
Folding of protein ● Protein folding is energetically favored reaction ● Components assisting folding could be needed (for example chaperones) & Caflisch (2000), PNAS 97,
Conformation vs. function ● Different conformations of the protein can have different functions ● Native state vs. functional state ● Protein activation Prion Biology and Diseases. Cold Spring Harbor Laboratory Press, NY, 1999.
Conformation vs. function ● Different conformations of the protein can have different functions ● Native state vs. functional state ● Protein activation Brain tissues showing amyloid plaques caused by aggregation of the particularly folded protein
Factors affecting protein conformation ● Physical parameters – temperature, pressure etc. ● Chemical parameters – pH, solvent electrophilicity etc. ● Mechanical force – force applied via interactions – force produced by the cell
Steered molecular dynamics ● Forced unfolding of protein ● NAMD molecular dynamics simulation ● 400 pN pulling force applied
Simulation methods ● Experimental protein structures used as a starting material ● Protein solvated in explicit water and ions added to neutralize the system ● Periodic water box used ● Typical system contains ~ atoms (~70-80% water) ● CHARMM27 force field used (Newtonian mechanics) ● NAMD simulation package (Developed by research group of Professor Klaus Schulten, ) ● Visualization of simulations with VMD
Computation ● Simulation carried out in femtosecond resolution ● Typical simulation time is some nanoseconds ● To obtain 1 ns simulation of atom system, ~24 hours simulation time is needed in Gonzales cluster using 64 processors ● Coordinates saved every ps -> 1 ns simulation produces about 2 GB of data. ● Atomic resolution of the protein and solvent behaviour
Conclusion ● Molecular dynamics simulations make it possible to study behaviour of proteins in equilibrium and non-equilibrium conditions ● We would like to study the role of mechanical signals in protein function regulation?
Computational research projects in the Professor Viola Vogel’s group ● Eileen Faucher – Functional properties of integrins ● John Saeger – Fluorescent proteins ● Lina Nilsson – Bacterial adhesion ● Vesa Hytönen – Dynamics of the focal contacts
Thank you!