[Chimera-users] Visualisation of membrane proteins

Elaine Meng meng at cgl.ucsf.edu
Tue Feb 14 09:31:49 PST 2017

Hi James,
(1) The easiest way to allow moving the ligand separately from the receptor is to put them in two different models. You could use the “split” command.  For example, if the structure is model #0 and your ligand is residue XYZ, command:

split #0 atoms :xyz


You would still need to delete any other stuff you didn’t want, like water molecules.  Or, you could open the same structure twice and in one copy, delete everything except your ligand, and in the second copy, delete everything except the receptor.  Then when you have two separate models, it is simple to move them separately.  Show Model Panel (from Favorites menu) and use the “A” checkboxes to deactivate (freeze) one while you move the other one with the mouse. 

You can also do fancy things like save different positions of the ligand and then show it moving from one position to another (see commands savepos, reset, and fly).

(2) there is no tool specifically to create some membrane representation.  However, I like to use the OPM database (Orientations of Proteins in Membranes) 
...which has downloadable PDB files of membrane proteins with additional fake atoms showing the estimated plane of the membrane.  If you open one of these you can see all the fake atoms, and you can show them as balls or, as I have done in this image, use the Chimera Axes/Planes/Centroids tool to show planes (discs) calculated from the fake atoms.

Your specific receptor may not be in this database, or even if it is, the coordinates may be moved.  However, if you get the OPM structure for that protein or just a related protein, you can use matchmaker to superimpose the two, and then hide the protein part of the OPM file, showing just the membrane representation.

I hope this helps,
Elaine C. Meng, Ph.D. 
UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab
Department of Pharmaceutical Chemistry
University of California, San Francisco

> On Feb 14, 2017, at 6:03 AM, James Starlight <jmsstarlight at gmail.com> wrote:
> Dear Chimera users!
> I am on the preparation of interactive molecular visualisation,
> focusing on ligand-binding representation in GPCRs system.
> Working with the X-ray structures of the receptor bound with the
> ligand, I wonder to ask some suggestions:
> 1 - I need to move ligand from ligand binding pocket burried within
> receptor (as on default in the X-ray structure) towards the selected
> position outside of it - e.g in case where I would like to depict
> "vestibule" for the ligand enterance. As I understood for the
> realisation  I should to select ligand within the current model and
> than to copy it to new model (layer) which then should be moved
> against the structure, shouldn't it?
> 2- Is it possible using some Chimera tool to indicate "approximate"
> membrane plane assuming that GPCRs structure is shown in latteral
> perspective?
> Thanks so much for the help!
> James

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