Nucleoporin 50kDa (NUP50)

Nucleoporin 50 kDa is a member of the FG-repeat containing nucleoporins that functions as a soluble cofactor in importin-alpha:beta-mediated nuclear protein import. Pseudogenes of this gene are found on chromosomes 5, 6, and 14. NUP50 is a tristable switch that alternates between binding modes.

The C terminus binds importin-beta through RAN-GTP. The N terminus binds the C terminus of importin-alpha, while a central domain binds importin-beta. NUP50:importin-alpha:importin-beta binds cargo and can stimulate nuclear import. Endogenous NUP50 can shuttle and is accessible from the cytoplasmic side of the nuclear envelope. These findings identified NUP50 as a cofactor for importin-alpha:importin-beta nuclear import and as a subunit of the importin complex.