Bingding Huang wrote: > I am new to Modeller. Now I want to fuse 3-residue peptide, for example > 3 Histine, to the N term of a structure-known protein like 2g2u, chain B. > Any idea about that?

This is very similar to question #1 in the FAQ: http://salilab.org/modeller/FAQ.html#1

If you don't have a structure for your tripeptide, you can certainly model it as an N-terminal insertion.

Ben Webb, Modeller Caretaker