Protein structure models based on X-ray crystallography data suggest that FENs have a flexible arch created by two α-helices through which the single 5' strand of the 5' flap structure can thread.
Os modelos de estrutura proteica baseados en datos de cristalografía de raios X suxiren que as FEN teñen un arco flexible creado por dúas hélices α a través do cal pode enfiarse a febra monocatenaria 5' da estrutura de solapa 5'.