Functional nuclear proteins are selectively imported into the nucleus by transport factors such as importins a and ß. Importin a, which mediates the nuclear import of nuclear localization signal (NLS)-containing proteins, is a member of nuclear transport factors. Importin a binds directly NLS and functions as an adapter for accessing the importin ß-dependent import pathway. The import complex is translocated through the nuclear pore complex by interactions of importin ß with a series of nucleoporins.Synonyms: Importin alpha Q2, Karyopherin subunit alpha-3, QIP2, SRP1-gamma