Abstract
BackgroundIron has an integral role in numerous cellular reactions and is required by virtually all organisms. In physiological conditions, iron is abundant in a largely insoluble ferric state. Ferric reductases are an essential component of iron uptake by cells, reducing iron to the soluble ferrous form. Cytochromes b561 (cyts-b561) are a family of ascorbate reducing transmembrane proteins found in most eukaryotic cells. The identification of the ferric reductase duodenal cytochrome b (dcytb) and recent observations that other cyts-b561 may be involved in iron metabolism have opened novel perspectives for elucidating their physiological function.Methodology/Principal FindingsHere we have identified a new member of the cytochrome b561 (Sjcytb561) family in the pathogenic blood fluke Schistosoma japonicum that localises to the outer surface of this parasitic trematode. Heterologous expression of recombinant Sjcyt-b561 in a Saccharomyces cerevisiae mutant strain that lacks plasma membrane ferrireductase activity demonstrated that the molecule could rescue ferric reductase activity in the yeast.Significance/ConclusionsThis finding of a new member of the cytochrome b561 family further supports the notion that a ferric reductase function is likely for other members of this protein family. Additionally, the localisation of Sjcytb561 in the surface epithelium of these blood-dwelling schistosomes contributes further to our knowledge concerning nutrient acquisition in these parasites and may provide novel targets for therapeutic intervention.
Highlights
Iron is an essential co-factor of many biological processes in most organisms, and serves as a major strengthening and stabilizing metal in invertebrates [1]
Chelators of ferric iron do not inhibit transmembrane iron transport and uptake, whereas ferrous chelators do [2,5]. This biological characteristic has led to the identification and functional characterization of many ferric reductases, molecules able to convert ferric to ferrous iron, from a wide range of organisms, most notably the well studied FRE family of metalloreductases of yeast and the ferric reductase oxidase (FRO) proteins of plants [6,7,8,9,10,11,12,13]
In view of Cytochrome b561 Ferric Reductase from Schistosomes. Parasites acquire their food from their hosts, either by feeding directly on tissues of the host, or by competing for ingested food
Summary
Iron is an essential co-factor of many biological processes in most organisms, and serves as a major strengthening and stabilizing metal in invertebrates [1]. Iron is predominantly stored or transported by an array of molecules, including organic chelates, the serum transporter transferrin, or in the cytoplasmic storage complex ferritin, in its ferric form [3,4]. It is in the divalent, or ferrous, state that iron participates as a co-factor in biological processes. The identification of the ferric reductase duodenal cytochrome b (dcytb) and recent observations that other cyts-b561 may be involved in iron metabolism have opened novel perspectives for elucidating their physiological function
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