GO_REF:0000002

Gene Ontology annotation through association of InterPro records with GO terms.

GO_REF:0000043

Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping

GO_REF:0000108

Automatic assignment of GO terms using logical inference, based on on inter-ontology links.

GO_REF:0000116

Automatic Gene Ontology annotation based on Rhea mapping.

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods.

PMID:18948262

Instability of superoxide dismutase 1 of Drosophila in mutants deficient for its cognate copper chaperone.

Ccs is the copper chaperone for SOD1 (dSod1) in Drosophila

"Copper is inserted into the SOD1 apoprotein by a specific chaperone, the copper chaperone for SOD1 (CCS)"
CCS-null mutants show loss of SOD1 activity and ~75% reduction in SOD1 protein levels

"the steady state level of SOD1 polypeptide in 29E is reduced to about one-quarter of its normal level in H340"
CCS-null flies have ~30% reduced median adult lifespan

"the absence of CCS confers early onset adult mortality with an ∼30% reduction in the median adult life span"
CCS-null flies are hypersensitive to paraquat (oxidative stress)

"29E displays the extreme toxic hypersensitivity to the redox cycling agent, paraquat, exhibited by SOD1-null"
Drosophila Ccs uniquely lacks the N-terminal MXCXXC copper-binding motif

"the domain I CXXC copper-binding motif is absent ... Of 20 CCS sequences analyzed from fungi to humans, only D. melanogaster and Anopheles gambiae lack the MXCXXC copper-binding site"
CCS stabilizes dSOD1 through copper insertion and/or disulfide oxidation

"apo-dSOD1 is unusually unstable and ... CCS affords stability to dSOD1 by activating the enzyme through copper insertion and/or disulfide oxidation"
dCCS can substitute for yeast CCS in activating SOD1

"Drosophila SOD1 exhibited no apparent preference for CCS and showed strong activation by both CCS molecules"
CCS-null flies show selective ~50% loss of cytosolic aconitase activity with no effect on mitochondrial aconitase

"cACON activity is selectively depleted by about 50% (H340 ∼1.6 × 29E), with no detectable affect on the activity of mACON"
CCS is composed of three domains - an N-terminal ATX1-like copper-binding domain I, a central SOD1-homology docking domain II, and a C-terminal domain III CXC copper site

"Finally the C-terminal domain III contains a critical CXC copper-binding site that inserts copper and oxidizes the intramolecular disulfide in SOD1"
Domain III cysteines Cys-229/Cys-231 are required for copper transfer and disulfide oxidation; a docking-deficient CCS or a C229S,C231S mutant fails to stabilize dSOD1

"C229S,C231S yCCS failed to stabilize dSOD1, indicating that copper transfer and/or disulfide oxidation are required"
Human SOD1 expressed in CCS-null flies is robustly active and rescues lifespan and oxidative stress deficits, indicating greater CCS-independent activation capacity than fly SOD1

"human SOD1 expressed in CCS-null flies is robustly active and rescues the deficits in adult life span and sensitivity to oxidative stress"
Drosophila CCS shows species-specific activation - poor at activating yeast SOD1 but nearly as effective as yeast CCS on human SOD1

"fly CCS was nearly as effective as yeast CCS in activating human SOD1"

PMID:22758915

An inventory of peroxisomal proteins and pathways in Drosophila melanogaster.

Ccs was identified in peroxisomes by proteomics analysis

"We have analyzed the proteome of Drosophila to identify the proteins involved in peroxisomal biogenesis and homeostasis as well as metabolic enzymes that function within the organelle"
Confirms cytoplasmic and peroxisomal localization

"The subcellular localization of five of these predicted peroxisomal proteins was confirmed"

file:DROME/Ccs/Ccs-deep-research-falcon.md

Falcon (Edison) deep research report: Functional annotation of Ccs (CG17753; UniProt A1Z850) in Drosophila melanogaster.

Ccs is a copper metallochaperone whose primary, experimentally supported function in Drosophila is post-translational activation and stabilization of cytosolic Cu,Zn-SOD1 (dSOD1), not catalysis of superoxide dismutation itself.

"The primary function of Drosophila Ccs is **post-translational activation and stabilization of cytosolic Cu,Zn-SOD1 (dSOD1)**, via copper delivery and associated maturation chemistry; in CCS-null flies, SOD1 activity becomes essentially undetectable and dSOD1 protein is strongly reduced"
CCS has a specialized post-translational maturation role rather than acting as the SOD catalytic enzyme itself; it delivers copper to apo-SOD1 and promotes formation of the mature active enzyme.

"CCS has a specialized **post-translational maturation role** rather than acting as the SOD catalytic enzyme itself: it **delivers copper to apo-SOD1** and promotes formation of the mature active enzyme."
Drosophila Ccs lacks the canonical N-terminal domain I MXCXXC copper-binding motif yet still supports SOD1 activation; the domain III CXC cysteines are required, as mutation abolished dSOD1 stabilization in yeast assays.

"A Drosophila-specific feature highlighted experimentally is that **Drosophila CCS lacks the canonical domain I MXCXXC copper-binding motif**, yet remains capable of supporting SOD1 activation"
CCS-null flies show selective depletion of cytosolic aconitase activity (~50%) with mitochondrial aconitase unaffected, consistent with loss of cytosolic SOD1 function.

"Cytosolic aconitase activity**: selectively depleted by **~50%**, while mitochondrial aconitase is unaffected"
CCS is catalytic relative to SOD1 (at least ~10x less abundant in molar terms) and matures SOD1 via copper insertion plus a disulfide-chemistry step involving transient CCS-SOD1 disulfide exchange.

"CCS is **catalytic** relative to SOD1, being at least **~10× less abundant** (molar) while efficiently maturing SOD1"
Drosophila Ccs shows species-specific activation: it activates Drosophila SOD1 well and is nearly as effective as yeast CCS on human SOD1, but is comparatively poor at activating yeast SOD1.

"it activates **Drosophila SOD1** well and is **nearly as effective as yeast CCS on human SOD1**, but is comparatively poor at activating **yeast SOD1**"
Direct subcellular localization of Drosophila Ccs protein was not retrieved; CCS-family reviews indicate CCS proteins are mainly cytosolic, with mitochondrial IMS localization in other systems treated as family-level inference.

"Broader CCS-family reviews indicate CCS proteins are mainly **cytosolic**, with additional localization to the **mitochondrial intermembrane space (IMS)** in other systems"
Glutathione can deliver copper to SOD1 when CCS is absent, providing a partial CCS-independent SOD1 activation route that explains why CCS-null phenotypes are milder than SOD1-null.

"the concept that GSH can deliver copper to SOD1 when CCS is absent"