The DOMON domains are involved in heme and sugar recognition

We expand the functionally uncharacterized DOMON domain superfamily to identify several novel families, including the first prokaryotic representatives. Using several computational tools we show that it is involved in ligand binding - either as heme- or sugar-binding domains. We present evidence that the DOMON domain along with the DM13 domain comprises a novel electron-transfer system potentially involved in oxidative modification of animal cell- surface proteins. Other novel versions might function as sugar sensors of histidine kinases of bacterial two component systems.