[chimerax-users] Superimpose overall structure

[Elaine Meng]

Dear Fengwei,
You're welcome!!   

If there were equal numbers of chains, you could specify multiple pairs of chains to fit with the "matchmaker" command option "pairing ss":
<http://rbvi.ucsf.edu/chimerax/docs/user/commands/matchmaker.html>
<http://rbvi.ucsf.edu/chimerax/docs/user/commands/matchmaker.html#options>

However, your situation where one structure has two chains and the other has three (but corresponding to a similar overall structure) is more complicated.  In that case the easy "matchmaker" approach, where it figures out the residue pairing for you by aligning the chain sequences, cannot be used.  Instead you would need to specify in the command line exactly which atoms to use for fitting, using the "align" command.  This is more difficult, since you will need to know exactly which residues in which chains of one structure should be overlaid with which residues in which chains of the other.
<http://rbvi.ucsf.edu/chimerax/docs/user/commands/align.html>

Command-line specification of chains, residues, atoms (scroll down for examples):
<http://rbvi.ucsf.edu/chimerax/docs/user/commands/atomspec.html#hierarchy>

I hope this helps,
Elaine
-----
Elaine C. Meng, Ph.D.                       
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco

> On Dec 10, 2020, at 1:22 PM, Zheng, Fengwei <Fengwei.Zheng at vai.org> wrote:
> 
> Dear ChimeraX developers,
> 
> Thank a bunch for developing this so gracious and powerful software for our community!
> 
> May I ask how to superimpose the overall structures of two analogues? e.g., the E. coli sliding clamp beta is a ring-shaped homodimer (two chains), while the yeast sliding clamp PCNA is a ring-shaped homotrimer (three chains), and their overall structures are quite similar, but when I use the matchmaker to superimpose them, it seems always only use the chain A, but not the all chains, pls see figures below~ Stay safe and warm, Many thanks!
> 
> <Outlook-bkctx0ak.png>
> Best,
> Fengwei