Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
Volume 1798, Issue 11, Pages 2131-2140Publisher
ELSEVIER
DOI: 10.1016/j.bbamem.2010.07.008
Keywords
Cyanobacterium; Copper and iron transport; Metal homeostasis; Siderophore secretion; TonB-dependent receptor
Categories
Funding
- Deutsche Forschungsgemeinschaft [DFG 585/2, SFB-TR01/C7]
- Volkswagenstiftung
- Boehringer Ingelheim Fonds
- EMBO
- Centre of Membrane Proteomics/Goethe University Frankfurt
- Ministerio de Educacion y Ciencia, Spain [BFU2008-03811]
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Iron uptake is essential for Gram-negative bacteria including cyanobacteria. In cyanobacteria, however, the iron demand is higher than in proteobacteria due to the function of iron as a cofactor in photosynthesis and nitrogen fixation, but our understanding of iron uptake by cyanobacteria stands behind the knowledge in proteobacteria. Here, two genes involved in this process in the heterocyst-forming cyanobacterium Anabaena sp. PCC 7120 were identified. ORF all4025 encodes SchE, a putative cytoplasmic membrane-localized transporter involved in ToIC-dependent siderophore secretion. Inactivation of schE resulted in an enhanced sensitivity to high metal concentrations and decreased secretion of hydroxamate-type siderophores. ORF all4026 encodes a predicted outer membrane-localized TonB-dependent iron transporter, lacT. Inactivation of iacT resulted in decreased sensitivity to elevated iron and copper levels. Expression of iacT from the artificial trc promoter (P-trc) resulted in sensitization against tested metals. Further analysis showed that iron and copper effects are synergistic because a decreased supply of iron induced a significant decrease of copper levels in the iacT insertion mutant but an increase of those levels in the strain carrying P-trc-iacT. Our results unravel a link between iron and copper homeostasis in Anabaena sp. PCC 7120. (C) 2010 Elsevier B.V. All rights reserved.
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