A novel homopolymeric phytoferritin from chickpea seeds with high stability

Abstract

Iron deficiency is a major public health problem in the world. Phytoferritin as an alternative iron supplement has received increasing attentions recently. Plant ferritins are usually heteropolymers comprising two different H-type subunits, H-1 and H-2, while homopolymeric plant ferritin is rare. In the present study, a newly homopolymeric ferritin chickpea seed ferritin (CSF) was isolated and purified to homogeneity from chickpea seed (Cicer arietinum L.) by two consecutive anion exchange and size exclusion chromatography. SDS-PAGE result indicates that CSF only consists of 28.0 kDa (H-2) subunits, which was identified by Western blot analysis as well. N-terminal sequence and MALDITOF-MS analyses indicate that the subunit of CSF and H-2 subunit of heteropolymeric pea seed ferritin (PSF) share high identity in amino acid sequence. Subsequently, we demonstrated that homopolymeric CSF exhibits a higher catalyzing activity than heteropolymeric PSF at both low and high iron loadings. More importantly, the stability of homopolymeric CSF is much higher than all known plant ferritin due to its highest H-2 subunit content, which is favorable for its application as iron supplement.