Nuclear transport factor 2 (NTF2) domain plays an important role in the trafficking of macromolecules, ions and small molecules between the cytoplasm and nucleus. This bi-directional transport of macromolecules across the nuclear envelope requires many soluble factors that includes GDP-binding protein Ran (RanGDP). RanGDP is required for both import and export of proteins and poly(A) RNA. RanGDP also has been implicated in cell cycle control, specifically in mitotic spindle assembly. In interphase cells, RanGDP is predominately nuclear and thought to be GTP bound, but it is also present in the cytoplasm, probably in the GDP-bound state. NTF2 mediates the nuclear import of RanGDP. NTF2 binds to both RanGDP and FxFG repeat-containing nucleoporins.