HGNC Approved Gene Symbol: HPX
Cytogenetic location: 11p15.4 Genomic coordinates (GRCh38): 11:6,431,049-6,440,987 (from NCBI)
Hemopexin is a plasma beta-glycoprotein that specifically binds one heme with high affinity and transports it to hepatocytes for salvage of iron (summary by Takahashi et al., 1985).
Takahashi et al. (1985) determined that human hemopexin consists of a single polypeptide chain of 439 amino acids and has a molecular mass of approximately 63 kD. Altruda et al. (1985) also determined the protein sequence of human hemopexin. Both groups noted that hemopexin is low in patients with hemolysis.
Naylor et al. (1987) found that hemopexin mRNA was present at a low level in fetal liver, increased dramatically in adult liver, and was not detectable in other tissues.
Altruda et al. (1988) demonstrated that the HPX gene spans approximately 12 kb and is interrupted by 9 exons. A direct correspondence between exons and the 10 repeating units in the protein was shown. The introns were not randomly placed; they fell in the middle of the region of amino acid sequence homology in strikingly similar locations in 6 of the 10 units and in a symmetric position in each half of the coding sequence. From these findings, Altruda et al. (1988) concluded that the gene evolved through intron-mediated duplications of a primordial sequence to a 5-exon cluster. A more recent gene duplication led to the present-day gene organization.
Cai and Law (1986) prepared a cDNA clone for hemopexin and, by Southern blot analysis of human/hamster hybrids containing different combinations of human chromosomes, assigned the hemopexin gene to human chromosome 11. Naylor et al. (1987) used a hemopexin cDNA clone to map the HPX gene to 11pter-p11 by somatic cell hybrid analysis. By means of in situ hybridization, Law et al. (1988) assigned the hemopexin gene to 11p15.5-p15.4, the same location as that of the beta-globin gene complex.
Hemopexin has been found in the serum of all mammals studied and it is polymorphic in rabbits. Stewart and Lovrien (1971) found no electrophoretic polymorphism in humans. Polymorphism of hemopexin is known in the pig (Lush, 1966). By isoelectric focusing, Kamboh and Ferrell (1987) demonstrated polymorphism of HPX in US blacks but not in US whites.
Data on gene frequencies of allelic variants were tabulated by Roychoudhury and Nei (1988).
Altruda, F., Poli, V., Restagno, G., Argos, P., Cortese, R., Silengo, L. The primary structure of human hemopexin deduced from cDNA sequence: evidence for internal, repeating homology. Nucleic Acids Res. 13: 3841-3859, 1985. [PubMed: 2989777] [Full Text: https://doi.org/10.1093/nar/13.11.3841]
Altruda, F., Poli, V., Restagno, G., Silengo, L. Structure of the human hemopexin gene and evidence for intron-mediated evolution. J. Molec. Evol. 27: 102-108, 1988. [PubMed: 2842511] [Full Text: https://doi.org/10.1007/BF02138368]
Cai, G.-Y., Law, M. L. Cloning and characterization of a human gene coding for hemopexin. (Abstract) Am. J. Hum. Genet. 39: A191 only, 1986.
Kamboh, M. I., Ferrell, R. E. Genetic studies of low-abundance human plasma proteins. VI. Polymorphism of hemopexin. Am. J. Hum. Genet. 41: 645-653, 1987. [PubMed: 3661561]
Law, M. L., Cai, G.-Y., Hartz, J. A., Jones, C., Kao, F.-T. The hemopexin gene maps to the same location as the beta-globin gene cluster on human chromosome 11. Genomics 3: 48-52, 1988. [PubMed: 3220477] [Full Text: https://doi.org/10.1016/0888-7543(88)90158-9]
Lush, I. E. The Biochemical Genetics of Vertebrates Except Man. Philadelphia: W. B. Saunders (pub.) 1966.
Naylor, S. L., Altruda, F., Marshall, A., Silengo, L., Bowman, B. H. Hemopexin is localized to human chromosome 11. Somat. Cell Molec. Genet. 13: 355-358, 1987. [PubMed: 3455011] [Full Text: https://doi.org/10.1007/BF01534930]
Roychoudhury, A. K., Nei, M. Human Polymorphic Genes: World Distribution. New York: Oxford Univ. Press (pub.) 1988.
Stewart, R. E., Lovrien, E. W. Haemopexin in human serum: a search for genetic polymorphism. Ann. Hum. Genet. 35: 19-24, 1971. [PubMed: 4105917] [Full Text: https://doi.org/10.1111/j.1469-1809.1956.tb01374.x]
Takahashi, N., Takahashi, Y., Putnam, F. W. Complete amino acid sequence of human hemopexin, the heme-binding protein of serum. Proc. Nat. Acad. Sci. 82: 73-77, 1985. [PubMed: 3855550] [Full Text: https://doi.org/10.1073/pnas.82.1.73]