[MMTK] Newby: Protein complex formation
Michiel Jan Laurens de Hoon
mdehoon at ims.u-tokyo.ac.jp
Wed Aug 20 18:33:43 EDT 2003
I am hoping to use MMTK to look at protein complex formation. To get
started, I loaded 1BON.pdb, which contains a sinI/sinR protein complex
of Bacillus subtilis, and ran MMTK's energy minimizer. I expected that
the minimizer would find a protein configuration that is close to what
is already in the PDB file. That seems to work, the protein
configurations change somewhat while the energy reduces from about
277000 to -20000.
Then, I used translateBy on each protein separately to put them a small
distance away from each other. Now I was hoping that the energy
minimizer would find something close to the initial protein complex.
That doesn't seem to work, the energy changes but the proteins do not
move towards each other.
So my questions are:
1) Is it at all possible what I am trying to do here? Or am I being too
2) In MMTK, do the proteins see each other, or are only forces internal
to the proteins included? I am using the Amber force field. If they
don't feel each other's force, what am I missing, and how can I include
3) Are the proteins treated as if they were in vacuum, or are they
assumed to be submerged in water?
Below is the Python script that I was using.
Thank you for your attention.
--Michiel, U Tokyo.
> from MMTK import *
> from MMTK.ForceFields import Amber94ForceField
> from MMTK.Minimization import SteepestDescentMinimizer
> from MMTK.Proteins import Protein
> from MMTK.Visualization import view
> complex = Protein('1B0N.pdb')
> sinR = copy(complex)
> sinI = copy(complex)
> difference = sinR.position() - sinI.position()
> print "initial distance:", difference
> universe = InfiniteUniverse(Amber94ForceField())
> minimizer = SteepestDescentMinimizer(universe, convergence=0)
> for i in range(10):
> print "Energy =", universe.energy(), "distance =", sinI.position()-sinR.position()
Michiel de Hoon
University of Tokyo, Institute of Medical Science
Human Genome Center
4-6-1 Shirokane-dai, Minato-ku
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