InterPro domain: IPR003829

This entry represents the Pirin N-terminal domain.

Eukaryotic pirins are highly conserved nuclear proteins that may function as transcriptional regulators with a role in apoptosis [ 1 , 2 ]. Prokaryotic homologues have also been identified. Both bacterial and human pirins have been shown to possess quercetinase activity [ 3 ], although this is not universally true for all family members - YhaK ( P42624 ), for example, displays no such enzymatic activity [ 4 ].

Pirin is composed of two structurally similar domains arranged face to face. Although the two domains are similar, the C-terminal domain of pirin differs from the N-terminal domain as it does not contain a metal binding site and its sequence does not contain the conserved metal-coordinating residues [ 5 ].

Pirin is considered a member of the cupin superfamily on the basis of primary sequence and structural similarity. The presence of a metal binding site in the N-terminal beta-barrel of pirin, may be significant in its interaction with Bcl-3 and nuclear factor I (NFI) and role in regulating NF-kappaB transcription factor activity [ 6 ].

1. Pirin inhibits cellular senescence in melanocytic cells. Am. J. Pathol. 178, 2397-406
2. A tomato homologue of the human protein PIRIN is induced during programmed cell death. Plant Mol. Biol. 46, 459-68
3. Structural and biochemical analysis reveal pirins to possess quercetinase activity. J. Biol. Chem. 280, 28675-82
4. The crystal structure of the protein YhaK from Escherichia coli reveals a new subclass of redox sensitive enterobacterial bicupins. Proteins 74, 18-31
5. Crystal structure of human pirin: an iron-binding nuclear protein and transcription cofactor. J. Biol. Chem. 279, 1491-8