Reptilian transferrins: Evolution of disulphide bridges and conservation of iron-binding center

Allelic discrimination, three-dimensional analysis and gene expression of multiple transferrin alleles of common carp (Cyprinus carpio L.)

“…Although carp Tf did not have equivalents to two disulphide bonds in human Tf and had one unique disulphide bond, the majority of the disulphide bonds were conserved in carp Tf. The putative existence of an intra-chain disulphide bond in cyprinid fish [8] was not supported by our modeling study. In general, the models confirmed the conserved three-dimensional structure of carp Tf.…”

“…An overall low conservation of iron binding residues in the N-lobe of Tf has been noted for all Cypriniformes fish species [8]. Indeed, of the six iron-coordinating residues in the N-lobe, only two residues are conserved in carp.…”

“…First, sequence information suggests that Tf of Cypriniformes fish might be partially nonfunctional owing to the substitution of important iron-coordinating residues in the N-lobe [8]. Second, in the absence of high concentrations of serum albumin, Tf of common carp has been recognized as the major protein for the transport of metals other than iron, such as cadmium [9].…”

Structure and expression of transferrin gene of channel catfish, Ictalurus punctatus

“…In oviparous vertebrates there is only one transferrin gene, expressed either in the liver as serum transferrin, or in the oviduct with a final localization in egg white as ovotransferrin [48,49]. For fish, transferrin seems to serve functionally as serum transferrin and lactoferrin, but the presence of melanotransferrin-like genes have also been reported in teleost species such as Fugu and tetraodon [50,51].…”

“…At the other three positions, the catfish transferrin gene harbors the same amino acids as in the mammalian species with Tyr-95, Tyr-188, and His-249. However, amino acids in these positions are variable in grass carp [48,52], zebrafish, and goldfish. In humans, mutation at Tyr-95 and Tyr-188 caused a dramatic reduction and complete loss of iron-binding [53].…”