Is a ferroxidase involved in the high-affinity iron uptake in Chlamydomonas reinhardtii?

• Published in: Plant and soil 2002-04, Vol.241 (1), p.1-9
• Main Authors: Herbik, Alexandra, Haebel, Sophie, Buckhout, Thomas J.
• Format: Article
• Language: English
• Subjects: Algae; Aquatic plants; Biological and medical sciences; Cell membranes; Centrifugation; Dunaliella; Fractionation; Fundamental and applied biological sciences. Psychology; Iron; Metabolism; Metabolism. Physicochemical requirements; Oxidases; Plant physiology and development; Plants; Proteins; Saccharomyces cerevisiae; Yeasts
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/A:1016037906516

In contrast to the halotolerant algae Dunaliella salina, Fe assimilation in the unicellular green algae Chlamydomonas reinhardtii involves a reductive step. After fractionation of proteins from Fe-sufficient and Fe-deficient cells, a distinct increase of a 150 kDa protein was observed in the Fe-deficient plasma membrane. The induction of the Fe3+ reductase activity and the 150 kDa protein under Fe deficiency was completely blocked by cycloheximide, indicating transcriptional regulation. After tryptic digestion, internal peptide sequences were obtained using MALDI-TOF MS. Based on the homology of these sequences to human hephaestin, a multicopper oxidase, which is involved in Fe homeostasis, the 150 kDa protein was named: ferroxidase-like protein (FLP). An oxidase activity measured as p-phenylenediamine oxidation, was also increased under Fe-deficiency, and this oxidase was inhibited by the inhibitor for multicopper oxidases, tetrathiomolybdate. Based on the physiological experiments and the homology in the primary structure of the ferroxidase-like protein to multicopper oxidases, we suggest that as in yeast and humans an oxidase is involved in the Fe uptake in C. reinhardtii.