InterPro domain: IPR004130

Proteins in this entry belong to the GPN-loop GTPase family [ 1 ], including Npa3 (also known as Gpn1) and Gpn2/3 from budding yeasts. In humans, Npa3 homologue is known as XAB1; Gpn2 is known as GPN2/ATPBD1B; Gpn3 is known as Parcs.

Npa3 plays an important part in transporting RNA polymerase II (RNAPII) to the nucleus. The binding of Npa3 with RNAPII is GTP-dependent [ 2 ]. Gpn2 and Gpn3 are putative GTPase that have a role in biogenesis of RNA polymerase II and III [ 3 ]. Npa3, Gpn2 and Gpn3 is involved in sister chromatid cohesion [ 4 , 5 ].

1. Structural insights into a new homodimeric self-activated GTPase family. EMBO Rep. 8, 569-75
2. GTP-dependent binding and nuclear transport of RNA polymerase II by Npa3 protein. J. Biol. Chem. 286, 35553-61
3. Biogenesis of RNA polymerases II and III requires the conserved GPN small GTPases in Saccharomyces cerevisiae. Genetics 193, 853-64
4. A role for GPN-loop GTPase yGPN1 in sister chromatid cohesion. Cell Cycle 10, 1828-37
5. Eukaryotic GPN-loop GTPases paralogs use a dimeric assembly reminiscent of archeal GPN. Cell Cycle 12, 463-72