Post-translational modifications of the AFET3 gene product: a component of the iron transport system in budding cells and mycelia of the yeast Arxula adeninivorans.
The yeast Arxula adeninivorans is characterized by a temperature-dependent dimorphism. A. adeninivorans grows as budding cells at temperatures up to 42 degrees C, but forms mycelia at higher temperatures. A strong correlation exists between morphological status and iron uptake, achieved by two transport systems that differ in iron affinity. In the presence of high Fe(II) concentrations (>2 microm), budding cells accumulate iron concentrations up to seven-fold higher than those observed in mycelia, while at low Fe(II) concentrations (<2 microm), both cell types accumulate similar amounts of iron. The copper-dependent Fe(II) oxidase Afet3p, composed of 615 amino acids, is a component of the high-affinity iron transport system. This protein shares a high degree of homology with other yeast iron transport proteins, namely Fet3p of Saccharomyces cerevisiae, Cafet3p of Candida albicans and Pfet3p of Pichia pastoris. Expression of the AFET3 gene is found to be strongly dependent on iron concentration but independent of the morphological stage; however, cell morphology was found to influence post-translational modifications of the gene product. O-glycosylation was observed in budding cells only, whereas N-glycosylation occurred in both cell types. The N-glycosylated 103 kDa glycoprotein matures into the 108.5 kDa form, further characterized by serine phosphorylation. Both N-glycosylation and phosphorylation occur at low iron concentrations (< or =5 microm). The mature Afet3p of 108.5 kDa is uniformly distributed within the plasma membrane in cells of both morphological stages.
Wartmann
Thomas
T
Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK), Corrensstrasse 3, D-06466 Gatersleben, Germany. kunzeg@ipk-gatersleben.de
Stephan
Udo W
UW
Bube
Ines
I
Böer
Erik
E
Melzer
Michael
M
Manteuffel
Renate
R
Stoltenburg
Regina
R
Guengerich
Laura
L
Gellissen
Gerd
G
Kunze
Gotthard
G
D000595:Amino Acid Sequence; D001203:Ascomycota / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000201:enzymology; D002570:Ceruloplasmin / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D006031:Glycosylation; D007150:Immunohistochemistry; D007501:Iron / Q000378:metabolism*; D008969:Molecular Sequence Data; D025282:Mycelium / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment
D029701:Saccharomyces cerevisiae Proteins; D007501:Iron; D002570:Ceruloplasmin; C085513:FET3 protein, S cerevisiae