Analysis of the Human Hephaestin Gene and Protein: Comparative Modelling of the N-terminus Ecto-domain Based Upon Ceruloplasmin

Hephaestin was implicated in mammalian iron homeostasis following its identification as the defective gene in murine sex-linked anaemia. It is a member of the family of copper oxidases that includes mammalian ceruloplasmin, factors V and VIII, yeast fet3 and fet5 and bacterial ascorbate oxidase. Hephaestin is different from ceruloplasmin, a soluble ferroxidase, in having a membrane-spanning region towards the C-terminus. Here we report the gene structure, spanning approximately 100 kb, of the human homologue of mouse hephaestin. The sequence was assembled from the cDNA clones and the chromosome X genomic sequence data available at the Sanger Centre. It has an open reading frame that encodes a protein of 1158 residues, 85% identical with the murine homologue. A model of the N-terminal ecto-domain has been built based on the known three-dimensional structure of human ceruloplasmin. The overall tertiary structure for the hephaestin and the putative residues involved in binding copper and iron appear to be highly conserved between these proteins, which suggests they share the same fold and a conserved function.