J. Biol. Chem., Vol. 259, Issue 1, 278-283, 01, 1984

Cell-specific properties of red cell and liver ferritin from bullfrog tadpoles probed by phosphorylation in vitro

K Ihara, K Maeguchi, CT Young and EC Theil

Cell-specific differences occur in the primary structure of ferritin. For example, red cell and liver ferritin from bullfrog tadpoles differ by 1.5 times in serine content. To determine if cell-specific differences in ferritin primary structure are expressed in the tetraeicosomer, which thus might distinguish the proteins in a functional state, phosphorylation in vitro was employed as a probe using [gamma-32P]ATP and the catalytic subunit from the cAMP-dependent protein kinase of bovine skeletal muscle. Subunits of both proteins in the tetraeicosomers were phosphorylated. Based on tryptic peptide maps, five regions common to both red cell and liver apoferritin were phosphorylated, as confirmed for two peptides by amino acid analyses. [32P]Apoferritin from red cells yielded an additional four 32P- fragments by mapping, at least three of which were unique by amino acid analysis and, in one case, might represent a 32P-Fe complex bound by a fragment of the iron-binding site. One peptide appeared to be unique to liver apoferritin. High concentrations of ATP yielded one additional peptide common to liver and red cell and one red cell-specific peptide in the tryptic peptide maps. The maximum moles of 32P/molecule were 13 +/- 4 and 6 +/- 2, respectively, for red cell and liver apoferritin, which corresponded within experimental error to the number of 32P- tryptic peptides. The level of phosphorylation was, on the average, not more than one site/subunit. Furthermore, above certain levels of phosphorylation, some subunits in the assemblage of 24 appeared to be unavailable as substrates, possibly because of charge repulsion or conformational changes. The possibility that post-translational modifications of ferritin which amplify cell-specific structural features occur in vivo with cytoplasmic components, e.g. protein kinases, is considered in terms of the physiological availability of iron from different iron storage cells and developmental changes in iron storage.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				X. Liu, W. Jin, and E. C. Theil Bioinorganic Chemistry Special Feature: Opening protein pores with chaotropes enhances Fe reduction and chelation of Fe from the ferritin biomineral PNAS, April 1, 2003; 100(7): 3653 - 3658. [Abstract] [Full Text] [PDF]

				T. Heise, A. Nath, K. Jungermann, and B. Christ Purification of a RNA-binding Protein from Rat Liver. IDENTIFICATION AS FERRITIN L CHAIN AND DETERMINATION OF THE RNA/PROTEIN BINDING CHARACTERISTICS J. Biol. Chem., August 8, 1997; 272(32): 20222 - 20229. [Abstract] [Full Text] [PDF]

				J. R. Suh, E. W. Oppenheim, S. Girgis, and P. J. Stover Purification and Properties of a Folate-catabolizing Enzyme J. Biol. Chem., November 3, 2000; 275(45): 35646 - 35655. [Abstract] [Full Text] [PDF]

				A. Caltagirone, G. Weiss, and K. Pantopoulos Modulation of Cellular Iron Metabolism by Hydrogen Peroxide. EFFECTS OF H2O2 ON THE EXPRESSION AND FUNCTION OF IRON-RESPONSIVE ELEMENT-CONTAINING mRNAs IN B6 FIBROBLASTS J. Biol. Chem., June 8, 2001; 276(23): 19738 - 19745. [Abstract] [Full Text] [PDF]