A specific role of the yeast mitochondrial carriers MRS3/4p in mitochondrial iron acquisition under iron-limiting conditions.
The yeast genes MRS3 and MRS4 encode two members of the mitochondrial carrier family with high sequence similarity. To elucidate their function we utilized genome-wide expression profiling and found that both deletion and overexpression of MRS3/4 lead to up-regulation of several genes of the "iron regulon." We therefore analyzed the two major iron-utilizing processes, heme formation and Fe/S protein biosynthesis in vivo, in organello (intact mitochondria), and in vitro (mitochondrial extracts). Radiolabeling of yeast cells with 55Fe revealed a clear correlation between MRS3/4 expression levels and the efficiency of these biosynthetic reactions indicating a role of the carriers in utilization and/or transport of iron in vivo. Similar effects on both heme formation and Fe/S protein biosynthesis were seen in organello using mitochondria isolated from cells grown under iron-limiting conditions. The correlation between MRS3/4 expression levels and the efficiency of the two iron-utilizing processes was lost upon detergent lysis of mitochondria. As no significant changes in the mitochondrial membrane potential were observed upon overexpression or deletion of MRS3/4, our results suggest that Mrs3/4p carriers are directly involved in mitochondrial iron uptake. Mrs3/4p function in mitochondrial iron transport becomes evident under iron-limiting conditions only, indicating that the two carriers do not represent the sole system for mitochondrial iron acquisition.
Mühlenhoff
Ulrich
U
Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Robert-Koch Str 6, 35033 Marburg, Germany.
Stadler
Jochen A
JA
Richhardt
Nadine
N
Seubert
Andreas
A
Eickhorst
Thomas
T
Schweyen
Rudolf J
RJ
Lill
Roland
R
Wiesenberger
Gerlinde
G
D000255:Adenosine Triphosphate / Q000378:metabolism; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000502:physiology*; D027682:Cation Transport Proteins; D003600:Cytosol / Q000378:metabolism; D017353:Gene Deletion; D016681:Genome, Fungal; D006418:Heme / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D020411:Oligonucleotide Array Sequence Analysis; D010957:Plasmids / Q000378:metabolism; D012097:Repressor Proteins / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology*; D015854:Up-Regulation
D002352:Carrier Proteins; D027682:Cation Transport Proteins; C066985:MRS3 protein, S cerevisiae; C066986:MRS4 protein, S cerevisiae; D024101:Mitochondrial Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D006418:Heme; D000255:Adenosine Triphosphate; D007501:Iron