Ribbon representations of GAP-oxidizing enzymes in Archaea. Ribbon representations of GAP-oxidizing enzymes in Archaea. (A) GAPN from Tpt. tenax (PDB accession number 1UXN) (174) showing the three-domain organization. GAPN is a member of the ALDH superfamily, also comprising the glyceraldehyde dehydrogenases from the npED branch in Thermoplasma spp. and α-ketoglutarate semialdehyde dehydrogenases from the pentose degradation pathway in Sulfolobus and Haloferax. (B) Aldehyde:ferredoxin oxidoreductase from Pyr. furiosus (PDB accession number 1AOR) (169), a representative of the AOR superfamily, to which the archaeal GAPORs also belong. The protein is organized in three domains, with the pterin cofactor and Fe/S cluster (depicted as a green stick model) binding site in the center between the three domains. (C) The classical GAPDH from Sul. solfataricus (PDB accession number 1B7G) (193) is shown operating exclusively in the anabolic/gluconeogenic direction, exhibiting the typical two-domain structure with an N-terminal Rossman fold nucleotide binding domain and a C-terminal catalytic domain. Christopher Bräsen et al. Microbiol. Mol. Biol. Rev. 2014; doi:10.1128/MMBR.00041-13