CRM1 (also known as Exportin1) mediates the nuclear export of proteins bearing a leucine-rich nuclear export signal (NES). CRM1 forms a complex with the NES containing protein and the small GTPase Ran. This region forms an alpha helical structure formed by six helical hairpin motifs that are structurally similar to the HEAT repeat, but share little sequence similarity to the HEAT repeat [1].

1: Architecture of CRM1/Exportin1 suggests how cooperativity is achieved during formation of a nuclear export complex. Petosa C, Schoehn G, Askjaer P, Bauer U, Moulin M, Steuerwald U, Soler-Lopez M, Baudin F, Mattaj IW, Muller CW; Mol Cell. 2004;16:761-775. PMID:15574331