Has an essential role during oogenesis and embryogenesis, perhaps in modulating the levels of nuclear import of additional proteins. Modulates the nuclear import of dorsal (dl), Dif and male specific lethal 1 (msl-1). Negatively regulates nuclear import of dl and controls the accumulation of dl in the nucleus after immune challenge. Homomultimer. Binds to dl and msl-1 via their nuclear localization signal (NLS). Also binds to Ran, Ran-like and mbo. Expressed both maternally and zygotically, zygotic expression is seen throughout development. 'Tamozhennic' means 'customs officer' in Russian. Contaminating sequence. Sequence of unknown origin in the N-terminal part.