Abstract:
Ferritins play an indispensable role in iron homeostasis through their iron-withholding function in living
beings. In the current study, cDNA sequences of three distinct ferritin subunits, including a ferritin H, a
ferritin M, and a ferritin L, were identified from big belly seahorse, Hippocampus abdominalis, and
molecularly characterized. Complete coding sequences (CDS) of seahorse ferritin H (HaFerH), ferritin M
(HaFerM), and ferritin L (HaFerL) subunits were comprised of 531, 528, and 522 base pairs (bp),
respectively, which encode polypeptides of 177, 176, and 174 amino acids, respectively, with molecular
masses of ~20e21 kDa. Our in silico analyses demonstrate that these three ferritin subunits exhibit the
typical characteristics of ferritin superfamily members including iron regulatory elements, domain signatures, and reactive centers. The coding sequences of HaFerH, M, and L were cloned and the corresponding proteins were overexpressed in a bacterial system. Recombinantly expressed HaFer proteins
demonstrated detectable in vivo iron sequestrating (ferroxidase) activity, consistent with their putative
iron binding capability. Quantification of the basal expression of these three HaFer sequences in selected
tissues demonstrated a gene-specific ubiquitous spatial distribution pattern, with abundance of mRNA in
HaFerM in the liver and predominant expression of HaFerH and HaFerL in blood. Interestingly, the basal
expression of all three ferritin genes was found to be significantly modulated against pathogenic stress
mounted by lipopolysaccharides (LPS), poly I:C, Streptococcus iniae, and Edwardsiella tarda. Collectively,
our findings suggest that the three HaFer subunits may be involved in iron (II) homeostasis in big belly
seahorse and that they are important in its host defense mechanisms
