Abstract:
Ferritins are biological iron chelators that can sequestrate excess iron to maintain iron homeostasis in the
body. Ferritins basically consist of 2 types of subunits, designated as H and L. However, another new
subunit, ferritin “M” which possesses characteristic features of both the H and L subunits, was recently
identified in lower vertebrates, mostly in fish. In this study, a ferritin M-like subunit from rock bream
(Oplegnathus fasciatus) (RbFerM) was characterized at the molecular level, and its transcriptional profile
was analyzed in healthy fish, as well as in pathogen- and mitogen-stimulated fish. Furthermore, its
functional properties were evaluated using the recombinant protein. The complete coding sequence of
RbFerM was 528 bp in length, encoding a 176-amino acid peptide with a calculated molecular mass of
20 kDa. In silico analysis of RbFerM revealed that it has features similar to both the mammalian ferritin
subunits, H and L. Phylogenetic analysis depicted the higher evolutionary proximity of RbFerM with its
fish counterparts. Quantitative real time polymerase chain reaction (PCR) analysis detected a ubiquitous
transcriptional profile of RbFerM in selected tissues of rock bream, in which more pronounced expression
was observed in blood and liver tissues. Significant transcriptional inductions of RbFerM were detected
in liver tissues upon lipopolysaccharides (LPS), Edwardsiella tarda, Streptococcus iniae, and rock bream
irido virus (RBIV) exposures in time-course immune-challenge experiments. The purified recombinant
protein of RbFerM demonstrated detectable iron chelating activity that varied with the temperature.
Moreover, the recombinant RbFerM rendered a detectable protection effect against iron (II) and H2O2-
mediated DNA damage.
