The NXF family of shuttling transport receptors for nuclear export of mRNA includes:

• vertebrate mRNA export factor TAP or nuclear RNA export factor 1 (NXF1).
• Caenorhabditis elegans nuclear RNA export factor 1 (nxf-1).
• yeast mRNA export factor MEX67.

Members of the NXF family have a modular structure. A nuclear localization sequence and a noncanonical RNA recognition motif (RRM) (see <PDOC00030>) followed by four LRR repeats are located in its N-terminal half. The C-terminal half contains a NTF2 domain (see <PDOC50177>) followed by a second domain. This most C-terminal TAP-C domain is important for binding to FG repeat-containing nuclear pore proteins (FG-nucleoporins) and is sufficient to mediate nuclear shuttling [1,2].

The Tap-C domain is made of four α helices packed against each other (see <PDB:1GO5>). The arrangement of helices 1, 2 and 3 is similar to that seen in a UBA fold. and is joined to the next module by flexible 12-residue Pro-rich linker [1,2].

The profile we developed covers the entire TAP-C domain.