[modeller_usage] homomultimers and symmetry

Hi there,

I am new to hands-on experience with Modeller. I would like to create a homology model of the protein that I am interested in as a homopentamer, using known homopentamer X-ray structures of related proteins. I have run across several questions in the archives about imposing symmetry constraints in the modeling process. Is it necessary to impose such constraints if the template is already a homopentamer with 5-fold symmetry? Doesn't this by itself impose symmetry constraints? Or, is it possible that an energy-minimized structure based on a symmetric template may not retain all of the symmetry of the template and the symmetry restraints make sure that the original symmetry is forced to be retained?

Finally, since model.symmetry.define() deals with pairs, does one enforce pentameric symmetry in the complex by forcing AB, BC, CD, DE, and EA symmetry, where A-E are the five individual subunits in the homopentamer?

Thanks

Mike White