Schematic representation of the FAD-binding and ALO domains found in full-length rat GULO (RfGULO), C-terminal rat L-gulono-γ-lactone oxidase (RcGULO), Arabidopsis GULLOs and L-galactono-γ lactone dehydrogenase (GalDH) from different plant sources. Domain sequences of individual proteins were obtained from conserved domains in the NCBI Protein database and compared to that of rat fGULO using the Global Align program. The length of the domains was drawn in relation to RfGULO, which is assumed to be 100%. The accession numbers of the sequences used are as follows: RfGULO (P10867.3), Arabidopsis homologs (AtGULLO1 to AtGULLO7), and GalDHs from Nicotiana tabacum (NtGalDH; BAB13368.1), Brassica oleracea (BoGalDH; O47881.1), Arabidopsis thaliana (AtGalDH; NP_190376.1), Ipomoea batatas (IbGalDH; BAA34995.1), and Solanum lycopersicum (SlGalDH; NP_001234603.1) [43,110].