Functions in nuclear protein import. Binds to importin subunit beta-1/KPNB1 via the IBB domain; this complex dissociates in the presence of RAN-GTP (By similarity). Binds to the NPM2 nuclear localization signal. Expressed almost exclusively in ovary, in germinal vesicle (GV)-stage oocytes, but not in granulosa, nor theca cells. Detected at very low levels in testis. Expressed at high levels in GV- and MII-stage oocytes, as well as in 2-cell embryos. Levels drop sharply by the blastocyst stage (at protein level). Not detectable in fetal ovaries 90 and 95 days of gestation, but highly abundant in fetal ovaries of late gestation. Belongs to the importin alpha family.