Two distinctly regulated genes are required for ferric reduction, the first step of iron uptake in Saccharomyces cerevisiae.

Abstract

Iron uptake in Saccharomyces cerevisiae involves at least two steps: reduction of ferric to ferrous ions extracellularly and transport of the reduced ions through the Iron is an indispensable element for living organisms. Oxygen storage and transport in plants and animals (leghemoglobins, hemoglobin, myoglobin, and hemerythrin), respiration, photosynthesis and electron transport (cytochromes), and nucleic acid metabolism (ribonucleotide reductase) are some examples of biological functions carried out principally by iron-containing proteins.Two features render iron an arduous metal to be handled by living organisms. The first is its availability; although it is the second most abundant metal in the earth's crust, iron is found primarily in the ferric (Fe3") state, forming hydroxides or salts of very low solubility and thus biologically inaccessible by simple mechanisms. The second is its toxicity; iron, in conjunction with oxygen, is a generator of hydroxyl radicals, which have a variety of toxic effects on cells.Living organisms as diverse as prokaryotes and mammals have developed a variety of mechanisms to overcome the problem of iron bioavailability as well as to regulate the iron concentration in biological fluids and cell compartments, in order to ensure its proper function as opposed to its toxic effects (reviewed in references 7 and 16). Two principal mechanisms have been described for iron uptake. One involves the use of iron chelators, either small molecules such as the siderophores secreted by bacteria, fungi, and plants or polypeptides such as transferrin and lactoferrin which are found in biological fluids of higher eukaryotes. All of these molecules keep ferric ions in a soluble form and deliver them to the cells mainly by receptor-mediated endocytosis. The second mechanism for iron uptake involves an initial reduction step in the external vicinity of the plasma membrane followed by internalization of the ferrous ions by means of ion transporters.Membrane-associated ferric reductase activity has been de-* Corresponding author. Mailing address:

Identification of the molecular mechanisms underlying the cytotoxic action of a potent platinum metallointercalator

“…The transport pathway was represented by 17 genes including FTR1, ARN1, ARN2, SIT1 (ARN3), ENB1 (ARN4), FRE1, FRE2, FRE3, FRE6, FIT2, FIT3, CTR1, CCC2, SIT1, PUG1, VMR1, DTR1 and RSB1. All of these genes except four (PUG1, VMR1, DTR1 and RSB1) are in the pathway of iron and copper transport across the cell membrane [24,30,49,57]. For example, FTR1 gene encodes a high-affinity iron permease for the transport of iron across the plasma membrane [69] and ARN1 encodes a membrane transporter responsible for up-taking iron bounded to siderophores [30].…”

Genetic engineering in the improvement of plants for phytoremediation of metal polluted soils

“…The same gene also restored a mutant (frd1-1) with de®cient copperchelate reduction. Two Fe(III) reductases, FRE1 and FRE2, have been isolated from S. cerevisiae (Dancis et al, 1990;Georgatsou and Alexandraki, 1994). Samuelsen et al (1998) …”

“…It was thus proposed that increase of the ferritin content of cereals by genetic modi®cation may help to solve the problem of dietary iron de®ciency. To increase the Fe content of rice, Goto et al (1999) transferred soybean ferritin gene into the plant. Using the rice seed storage protein glutelin promoter (GluB-1), they could target the expression of ferritin in developing seeds.…”

Siderophore uptake by Candida albicans: effect of serum treatment and comparison with Saccharomyces cerevisiae

“…S. cerevisiae can use two different high-affinity mechanisms, reductive and non-reductive, to take up iron from the extracellular medium (De Luca and Wood, 2000). The reductive mechanism (Dancis et al, 1990;Lesuisse et al, 1987) involves the release of extracellular ferric chelates by reduction at the cell surface by the inducible plasma membrane reductases, Fre1p and Fre2p (Dancis et al, 1992;Georgatsou and Alexandraki, 1994). A permease-oxidase complex, Ftr1p and Fet3p, is than involved in translocating iron through the plasma membrane (Askwith et al, 1994;Stearman et al, 1996).…”