Protein exceeds max number of atoms

Hi, I want to dock a protein on E. coli RNA polymerase subunits.
However, the following error message occurs
“The second PDB exceeds the maximum number of atoms allowed on this system”

I am wondering how large is the max number of atoms for the system.
I am using the easy interface.
Is there anyway to change the default settings, perhaps in expert or guru interface?

Thanks,
Pin-Kuang

Because of the computational costs we indeed limit the maximum number of atoms.
The current limit is 50000.

The question is: Do you need the full RNA polymerase? If you protein only interacts with a few domains, leave the others out.