Structural and functional analyses of chicken liver ferritin

Abstract

Characterization of ferritins from different species has provided insight into iron regulation mechanisms and evolutionary relationships. Here, we examined chicken liver ferritin, which comprises only H subunit and has 14.8 µg of Fe/100 µg of protein. The chicken H subunit apo homopolymer showed the same iron uptake rate as bovine H subunit homopolymer expressed with a baculovirus expression system (0.31 and 0.28 mmol of Fe/min per micromole of protein for chicken and bovine H subunit, respectively). Chicken H subunit apo homopolymer showed a significantly higher biotinylated hemin-binding activity than liver holoferritin. Although bovine spleen apoferritin, which has an L (liver or light):H (heart or heavy) subunit ratio of 1:1, also shows a significantly higher biotinylated hemin-binding activity than its holoferritin, these biotinylated hemin-binding activities were markedly lower than those of both chicken holo- and apoferritins. Binding of chicken holo- and apoferritin with biotinylated hemin was strongly inhibited by hemin but not iron-free hemin, protoporphyrin IX, or Zn-protoporphyrin. These findings demonstrate that chicken ferritin comprises only an H subunit, possesses ferroxidase activity as in mammalian ferritin H subunits, and binds heme more strongly than mammalian ferritins.

Binding Analysis of Ferritin with Heme Using α-Casein and Biotinylated-Hemin: Detection of Heme-Binding Capacity of Dpr Derived from Heme Synthesis-Deficient <i>Streptococcus mutans</i>

“…The binding of both of these proteins to coated α-casein was inhibited by hemin. These findings agree with the previous results showing that the H subunit has higher affinity to hemin than the L subunit [13,23], and that the binding of ferritin with α-casein is heme-mediated [22]. In addition, with the use of α-casein-immobilized beads, it is possible to obtain more iron-or heme-binding protein than The ferritins bound to the well were detected with biotinylated antibody to commercial horse spleen ferritin and ALP-labeled avidin.…”

“…Mammalian, avian and bacterial ferritins bind heme [8,9,13,23]. Mammalian ferritin H subunits are likely to preferentially bind heme as compared with L subunits [13,23].…”

“…Mammalian ferritin H subunits are likely to preferentially bind heme as compared with L subunits [13,23]. Avian species are known to express only the H subunit, and chicken H subunit homopolymers bind more heme than the mammalian ferritins [13,23].…”

“…Mammalian ferritins are 24-mer proteins, composed of two types of subunits named the H (heart or heavy) and L (liver or light) subunits [1,5,15,20]. Chicken and bacterial ferritin subunits possess ferroxidase activity (iron-binding site) as in mammalian H subunits [1,3,7,13,23].…”

“…Mammalian ferritin H subunits are likely to preferentially bind heme as compared with L subunits [13,23]. Avian species are known to express only the H subunit, and chicken H subunit homopolymers bind more heme than the mammalian ferritins [13,23]. Bacterial DNA-binding protein from starved cells (Dps) is a decameric iron-binding protein that belongs to the ferritin superfamily, and its iron-binding capacity protects DNA from oxidative stress [11,12].…”