In a cell free system , binding of a protein fragment ( 175 475 ) bound to __NODE__ and containing a ligand binding domain from __SP__ __NODE__ protein and a protein fragment ( 431 1158 ) from __SP__ __NODE__ protein is the same as binding of a protein fragment ( 175 475 ) bound to __NODE__ and containing a ligand binding domain from __SP__ __NODE__ protein and a protein fragment ( 951 1158 ) from __SP__ __NODE__ protein .