NTF2 only bind to Ran-GDP, not Ran-GTP. They form complex by 1:1 ratio. Ran E is resulting from fortuitous packing in the crystals. Here we only focus on the interface of NTF2 B and Ran C-GDP.

Click to see the interface of NTF2 and Ran-GDP on the Ran Part

The residues in Ran-GDP that interact with NTF2 are located primarily within the loop containing residues 65 to 78 (G3 or called SWITCH II) together a minor involvement of 39 to 43 (G2 or called SWITCH I). This two region change dramatically in their conformation between GDP and GTP-bound forms. (Sorry! Ran-GTP is not available now. See (ref. 6 for latest details on Ran bound to a GTP analogue/Ran-GppNHp)

Click to see the interface of NTF2 and Ran-GDP on the NTF2 Part

Hydrophobic residues in the upper portion of the NTF2 cavity, together with negatively charged residues surrounding the cavity (Glu42, Asp92, Asp94) and the C terminus (residues 121-124) made significant contributions to the interface with Ran-GDP (charged residues and C terminus are showed by ball and stick form).

Click to see the most important residue of Ran-GDP (Phe72)

The aromatic ring of Phe72 of Ran inserted into the hydrophobic cavity of NTF2 where it is surrounded by the hydrophobic sidechains of Trp41, Leu59, Phe61, Ile64, Leu89, Ala91, Met97, Phe119 and Lue121. The total buried surface area of the interface between each pair of chains is 1640 Ų, of which 22% (365 Ų) was attributable to Ran Phe72.

Click to see buried residues

On Ran, residues Ala67, Gly68, Gln69, Phe72 and Gly78 are buried in the interaction interface, whereas on NTF2 Trp41, Leu59, Phe61, Ile64, Met97, Gly98, Leu121, Ala122, Leu123 and His124 are buried.

Click to see salt bridge I

Click to see salt bridge II

There are salt bridges between NTF2 Glu42 and Ran Arg76 and between Ran Lys71 and NTF2 Asp92 and Asp94.

Click to see the potential hydrogen bond between NTF2 and Ran-GDP

There is a potential hydrogen bond with good geometry between the backbones of Ran Thr42 and NTF2 His124.