XPO5

[5][6][7] In eukaryotic cells, the primary purpose of XPO5 is to export pre-microRNA (also known as pre-miRNA) out of the nucleus and into the cytoplasm, for further processing by the Dicer enzyme.

This helps the backbone phosphates of these two nucleotides form hydrogen bonds with many XPO5 residues, allowing XPO5 to recognize the RNA as pre-miRNA.

Because these interactions involve only the RNA phosphate backbone, they are nonspecific and allow XPO5 to recognize and transport any pre-miRNA.

The rest of the pre-miRNA stem binds to XPO5 via interactions between the negatively-charged phosphate backbone and several positively-charged interior XPO5 residues.

[15] It has been suggested, through evidence provided by contour maps of water density, that the interior of XPO5 is hydrophilic, while the exterior of XPO5 is hydrophobic.

Image of XPO5 ternary complex generated in PyMol from crystal structure entry 3A6P in the Protein Data Bank. XPO5 is labeled green, Ran is labeled red, RNA is multi-colored, and GTP is labeled white. [ 14 ]