Two Chlamydomonas CTR Copper Transporters with a Novel Cys-Met Motif Are Localized to the Plasma Membrane and Function in Copper Assimilation

Abstract

Inducible high-affinity copper uptake is key to copper homeostasis in Chlamydomonas reinhardtii. We generated cDNAs and updated gene models for four genes, CTR1, CTR2, CTR3, and COPT1, encoding CTR-type copper transporters in Chlamydomonas. The expression of CTR1, CTR2, and CTR3 increases in copper deficient cells and in response to hypoxia or Ni2+ supplementation; this response depends on the transcriptional activator CRR1. A copper response element was identified by mutational analysis of the 5′ upstream region of CTR1. Functional analyses identify CTR1 and CTR2 as the assimilatory transporters of Chlamydomonas based on localization to the plasma membrane and ability to rescue a Saccharomyces cerevisiae mutant defective in high-affinity copper transport. The Chlamydomonas CTRs contain a novel Cys-Met motif (CxxMxxMxxC-x5/6-C), which occurs also in homologous proteins in other green algae, amoebae, and pathogenic fungi. CTR3 appears to have arisen by duplication of CTR2, but CTR3 lacks the characteristic transmembrane domains found in the transporters, suggesting that it may be a soluble protein. Thus, Chlamydomonas CTR genes encode a distinct subset of the classical CTR family of Cu(I) transporters and represent new targets of CRR1-dependent signaling.

Early eukaryotic origins for cilia-associated bioactive peptide-amidating activity

“…Supplying ascorbate and copper to the lumen of the secretory pathway requires transporters. The copper-handling machinery in Chlamydomonas is similar to that in all eukaryotic cells (Merchant et al, 2006;Page et al, 2009;Blaby-Haas and Merchant, 2012). Cytosolic chaperones deliver the copper they receive from plasma membrane transporters to two highly conserved copper-transporting P-type ATPases.…”

The Bacterial Pathogen Xanthomonas oryzae Overcomes Rice Defenses by Regulating Host Copper Redistribution

“…Previous studies have reported that a single Ctr-or COPT-type plasma membrane-localized protein from human (hCtr1; Zhou and Gitschier, 1997), yeast (Sc Ctr3; Pena et al, 2000), mouse (mCtr1; Lee et al, 2000), Arabidopsis (COPT1, 2, 3, and 5; Kampfenkel et al, 1995;Sancenó n et al, 2004), lizard (Ctr1; Riggio et al, 2002), Drosophilia melanogaster (Ctr1A, B, and C; Zhou et al, 2003), or Chlamydomonas reinhardtii (CTR1 and 2; Page et al, 2009) can complement the phenotype of S. cerevisiae ctr1Dctr3D mutant. Rice COPT1 and COPT5, which harbor the conserved motifs and residues required for Cu transport (Puig et al, 2007), have 21 to 51% sequence identity and 35 to 68% sequence similarity with these Ctr or COPT proteins (see Supplemental Table 3 online).…”

“…There are multiple members of the COPT (copper transporter) protein family that act in Cu homeostasis by Cu uptake in each analyzed plant species (Kampfenkel et al, 1995;Sancenó n et al, 2004;Page et al, 2009). These COPTs are the homologs of yeast and human Ctr (copper transporter) proteins (Sancenó n et al, 2003;Page et al, 2009). Some Ctrs can interact with themselves or with other Ctr proteins to mediate Cu uptake toward the cytosol (Zhou and Thiele, 2001;Lee et al, 2002;Beaudoin et al, 2006;Nose et al, 2006).…”

“…There are multiple members of the COPT (copper transporter) protein family that act in Cu homeostasis by Cu uptake in each analyzed plant species (Kampfenkel et al, 1995;Sancenó n et al, 2004;Page et al, 2009). These COPTs are the homologs of yeast and human Ctr (copper transporter) proteins (Sancenó n et al, 2003;Page et al, 2009).…”

Genetically Programmed Changes in Photosynthetic Cofactor Metabolism in Copper-deficient Chlamydomonas

“…Its homologue in Arabidopsis, SPL7, controls nutritional copper homeostasis as well (7,8). Transcriptome experiments revealed multiple targets of this transcription factor in both organisms but besides the genes encoding assimilatory copper transporters (COPT/CTR), which are dramatically up-regulated in both organisms under copper deficiency (9,10), the target genes are distinct (8,11). This may be because modification of the photosynthetic apparatus is a key response in Chlamydomonas but not in Arabidopsis.…”