 Members of the importin-β family can bind and transport cargo by themselves, or can form heterodimers with importin-α.As part of a heterodimer, importin-β mediates interactions with the pore complex, while importin-α acts as an adaptor protein to bind the nuclear localisation signal (NLS) on the cargo.The NLS-Importin α-Importin β trimer dissociates after binding to Ran GTP inside the nucleus, with the two importin proteins being recycled to the cytoplasm for further use.