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Proc Natl Acad Sci U S A. 2015 Mar 3;112(9):2644-51. doi: 10.1073/pnas.1422492112. Epub 2015 Feb 2.

Copper economy in Chlamydomonas: prioritized allocation and reallocation of copper to respiration vs. photosynthesis.

Author information

1
Department of Chemistry and Biochemistry, and.
2
Institute for Integrated Research in Materials, Environments, and Societies, California State University, Long Beach, CA 90840.
3
Department of Chemistry and Biochemistry, and Institute for Genomics and Proteomics, University of California, Los Angeles, CA 90095; and sabeeha@chem.ucla.edu.

Abstract

Inorganic elements, although required only in trace amounts, permit life and primary productivity because of their functions in catalysis. Every organism has a minimal requirement of each metal based on the intracellular abundance of proteins that use inorganic cofactors, but elemental sparing mechanisms can reduce this quota. A well-studied copper-sparing mechanism that operates in microalgae faced with copper deficiency is the replacement of the abundant copper protein plastocyanin with a heme-containing substitute, cytochrome (Cyt) c6. This switch, which is dependent on a copper-sensing transcription factor, copper response regulator 1 (CRR1), dramatically reduces the copper quota. We show here that in a situation of marginal copper availability, copper is preferentially allocated from plastocyanin, whose function is dispensable, to other more critical copper-dependent enzymes like Cyt oxidase and a ferroxidase. In the absence of an extracellular source, copper allocation to Cyt oxidase includes CRR1-dependent proteolysis of plastocyanin and quantitative recycling of the copper cofactor from plastocyanin to Cyt oxidase. Transcriptome profiling identifies a gene encoding a Zn-metalloprotease, as a candidate effecting copper recycling. One reason for the retention of genes encoding both plastocyanin and Cyt c6 in algal and cyanobacterial genomes might be because plastocyanin provides a competitive advantage in copper-depleted environments as a ready source of copper.

KEYWORDS:

RNA-seq; acclimation; copper homeostasis; copper store; metal

PMID:
25646490
PMCID:
PMC4352834
DOI:
10.1073/pnas.1422492112
[Indexed for MEDLINE]
Free PMC Article

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