In a cell free system , binding of a double stranded DNA fragment containing a __NODE__ response sequence from __NODE__ gene and a protein fragment ( 160 266 ) containing a alpha helix 1 3 and a DNA binding domain from mutant __NODE__ protein ( S256A ) is the same as binding of a double stranded DNA fragment containing a __NODE__ response sequence from __NODE__ gene and a protein fragment ( 160 266 ) containing a alpha helix 1 3 and a DNA binding domain from __NODE__ protein .