title: The P174L mutation in human Sco1 severely compromises Cox17-dependent metallation but does not impair copper binding.
abstract: Sco1 is a metallochaperone that is required for copper delivery to the Cu(A) site in the CoxII subunit of cytochrome c oxidase. The only known missense mutation in human Sco1, a P174L substitution in the copper-binding domain, is associated with a fatal neonatal hepatopathy; however, the molecular basis for dysfunction of the protein is unknown. Immortalized fibroblasts from a SCO1 patient show a severe deficiency in cytochrome c oxidase activity that was partially rescued by overexpression of P174L Sco1. The mutant protein retained the ability to bind Cu(I) and Cu(II) normally when expressed in bacteria, but Cox17-mediated copper transfer was severely compromised both in vitro and in a yeast cytoplasmic assay. The corresponding P153L substitution in yeast Sco1 was impaired in suppressing the phenotype of cells harboring the weakly functional C57Y allele of Cox17; however, it was functional in sco1delta yeast when the wild-type COX17 gene was present. Pulse-chase labeling of mitochondrial translation products in SCO1 patient fibroblasts showed no change in the rate of CoxII translation, but there was a specific and rapid turnover of CoxII protein in the chase. These data indicate that the P174L mutation attenuates a transient interaction with Cox17 that is necessary for copper transfer. They further suggest that defective Cox17-mediated copper metallation of Sco1, as well as the subsequent failure of Cu(A) site maturation, is the basis for the inefficient assembly of the cytochrome c oxidase complex in SCO1 patients.
authors.affiliation: Department of Medicine, University of Utah Health Sciences Center, Salt Lake City, Utah 84132, USA.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Cobine
authors.forename: Fabien
authors.initials: F
authors.lastname: Pierrel
authors.forename: Scot C
authors.initials: SC
authors.lastname: Leary
authors.forename: Florin
authors.initials: F
authors.lastname: Sasarman
authors.forename: Yih-Chern
authors.initials: YC
authors.lastname: Horng
authors.forename: Eric A
authors.initials: EA
authors.lastname: Shoubridge
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Winge
mesh_terms: D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D000079922:Copper Transport Proteins; D003576:Electron Transport Complex IV / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000172:deficiency* / Q000235:genetics / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism; D018832:Molecular Chaperones; D009154:Mutation; D020125:Mutation, Missense; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry
chemical_list: C491006:COX17 protein, human; D002352:Carrier Proteins; D000079922:Copper Transport Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D011994:Recombinant Proteins; C489345:SCO1 protein, human; D003300:Copper; C117108:cytochrome C oxidase subunit II; D003576:Electron Transport Complex IV