InterPro domain: IPR006502

This family of uncharacterised plant proteins are defined by a region found toward the C terminus. This region is strongly conserved (greater than 30 % sequence identity between most pairs of members) but flanked by highly divergent regions including stretches of low-complexity sequence.

PDDEXK_6 is a family of plant proteins that are distant homologues of the PD-(D/E)XK nuclease superfamily. The core structure is retained, as alpha-beta-beta-beta-alpha-beta. It retains the characteristic PDDEXK motifs II and III in modified forms - xDxxx motif located in the second core beta-strand, where x is any hydrophobic residue, and a D/E)X(D/N/S/C/G) pattern. The missing positively charged residue in motif III is possibly replaced by a conserved arginine in motif IV located in the proceeding alpha-helix [ 1 ]. The family is not in general fused with any other domains, so its function cannot be predicted [ 2 ].

1. Realm of PD-(D/E)XK nuclease superfamily revisited: detection of novel families with modified transitive meta profile searches. BMC Struct. Biol. 7, 40
2. Conserved Peptide Upstream Open Reading Frames are Associated with Regulatory Genes in Angiosperms. Front Plant Sci 3, 191