Aerobic Cyclase System Fe-containing subunit (ACSF), ferritin-like diiron-binding domain
Aerobic Cyclase System, Fe-containing subunit (ACSF) is a member of a broad superfamily of ferritin-like diiron-carboxylate proteins. Rubrivivax gelatinosus acsF codes for a conserved, putative binuclear iron-cluster-containing protein involved in aerobic oxidative cyclization of Mg-protoporphyrin IX monomethyl ester. AcsF and homologs have a leucine zipper and two copies of the conserved glutamate and histidine residues predicted to act as ligands for iron in the Ex(29-35)DExRH motifs. Several homologs of AcsF are found in a wide range of photosynthetic organisms, including Chlamydomonas reinhardtii Crd1 and Pharbitis nil PNZIP, suggesting that this aerobic oxidative cyclization mechanism is conserved from bacteria to plants.