A transferrin-like protein that does not bind iron is induced by iron deficiency in the alga Dunaliella salina

Michal Schwarz, Neta Sal-Man, Ada Zamir, Uri Pick

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Iron deficiency induces two major transferrin-like proteins in the plasma membrane (Pm) of the halotolerant alga Dunaliella salina. TTf, a 150-kDa protein, previously identified as a salt-induced triplicated transferrin, having iron-binding characteristics resembling animal transferrins, and a 100-kDa protein designated idi-100 (for iron-deficiency-induced 100 kDa protein). According to the predicted amino acid sequence of idi-100, it is only 30% identical to TTf and differs from it in having two, rather than three, homologous internal repeats and in a lower conservation of canonical iron/bicarbonate binding residues. Both are localized in the outer surface of the membrane; however, TTf can be dissociated from the membrane by treatment with EDTA, whereas release of idi-100 requires detergents. The accumulation of idi-100 under iron deficiency lags behind that of TTf and in contrast to TTf, it is not induced by high salinity, suggesting that induction of idi-100 requires lower Fe threshold levels than that of TTf. In contrast to TTf, idi-100 does not bind Fe; however, there are indications for interactions with bicarbonate ions. These results suggest that despite their common resemblance to transferrins, their similar subcellular localization and their induction by iron deficiency, idi-100 and TTf fulfill different functions.

Original languageEnglish
Pages (from-to)190-200
Number of pages11
JournalBiochimica et Biophysica Acta - Proteins and Proteomics
Volume1649
Issue number2
DOIs
StatePublished - 30 Jul 2003
Externally publishedYes

Keywords

  • Alga
  • Dunaliella
  • Iron deficiency
  • Iron-binding
  • Transferrin

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biophysics
  • Biochemistry
  • Molecular Biology

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