9571. Transferrins

Description and references

A group of homologous non-heme, iron-binding glycoproteins of approx mol wts of 76,000-81,000. They are widely distributed in a variety of physiological fluids and cells, esp in the sera of most vertebrates, in egg whites and in mammalian milk, tears and leukocytes. They are involved in iron transport to developing red cells for hemoglobin synthesis. Each protein molecule specifically binds with two Fe3+ ions to form salmon-pink complexes; bicarbonate or carbonate ions are involved in the formation of these colored complexes. Reviews of isoln, properties and biological functions: Feeney, Komatsu, Struct. Bonding 1, 149-206 (1966); Aisen, “The Transferrins” in Inorganic Biochemistry vol. 1, G. L. Eichhorn, Ed. (Elsevier, New York, 1973) pp 280-305; Bezkorovainy, Zschocke, Arzneim.-Forsch. 24, 476-485, 726-737 (1974); P. Aisen, A. Leibman, Bioinorg. Chem. II, K. N. Raymond, Ed. (A.C.S., Washington, 1977) pp 104-126; P. Aisen, I. Listowsky, Annu. Rev. Biochem. 49, 357-393 (1980). Review of transferrin receptors: R. Newman et al., Trends Biochem. Sci. 7, 397-399 (1982).

Derivative

Serum transferrin.

Nomenclature

β1-Metal-combining protein; siderophilin.

Properties

Commonly called transferrin. Structure of carbohydrate moiety: Jamieson et al., J. Biol. Chem. 246, 3686 (1971). Composed of two homologous domains, each containing a binding site for metal ions. The sites are similar, but not identical, in their metal-binding properties. X-ray studies: L. J. DeLucas et al., J. Mol. Biol. 123, 285 (1978). Resolution of the two sites by Eu(III) excitation spectroscopy: P. B. O'Hara, R. Bersohn, Biochemistry 21, 5269 (1982). N-Terminal amino acid sequence of human serum transferrin: M.-H. Metz-Boutigue et al., Biochim. Biophys. Acta 670, 243 (1981). Absorption max of human serum Fe3+-transferrin: about 465 nm (E1%1cm 0.57); uv max: 280 nm (E1%1cm 14.3).

Derivative

Conalbumin.

Nomenclature

Ovotransferrin; Diarconal (Recordati).

Description and references

Isolated from egg white; distinguished from ovalbumin by its lower thermal coagulation point: Osborne, Campbell, J. Am. Chem. Soc. 22, 422 (1900). Sepn from other egg-white proteins: Longworth et al., ibid. 62, 2580 (1940). Primary structure of hen ovotransferrin: J. Williams et al., Eur. J. Biochem. 122, 297 (1982). Purification, characterization and function of the iron-binding fragments: W.-M. Keung et al., J. Biol. Chem. 257, 1177, 1184 (1982). Antibacterial activity: P. Valenti et al., Antimicrob. Agents Chemother. 21, 840 (1982).

Properties

Absorption max of Fe3+-complex: 470 nm (E1%1cm 0.62).

Derivative

Lactoferrin.

Nomenclature

Lactotransferrin.

Description and references

Important component of the human milk bacteriostatic system; also found in human and bovine tear proteins. Isoln from human whey by a single chromatographic step: L. Blckberg, O. Hernell, FEBS Lett. 109, 180 (1980). Sequential purification of lactoferrin, lysozyme, and secretory IgA from human milk: M. Boesman-Finkelstein, R. A. Finkelstein, ibid. 144, 1 (1982). Partial C-terminal amino acid sequence of human lactoferrin: M.-H. Metz-Boutigue et al., ibid. 142, 107 (1982).