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The P(174)L mutation in the human hSCO1 gene affects the assembly of cytochrome c oxidase
C Paret1, A Lode, U Krause-Buchholz
1Institute of Genetics, University of Technology Dresden, Mommsenstrasse 13, Dresden, D-01062, Germany.
Insights
Human SCO1 gene mutations cause neonatal ketoacidotic coma and COX deficiency. The P(174)L mutation severely impairs cytochrome c oxidase (COX) assembly and activity, confirming its pathogenic role.
Area of Science:
- Biochemistry
- Genetics
- Molecular Biology
Background:
- Mutations in the yeast SCO1 gene lead to impaired cytochrome c oxidase (COX) assembly.
- Heterozygous mutations in the human homologue hSCO1 are linked to neonatal ketoacidotic coma and isolated COX deficiency.
- Identified mutations include a frameshift and a missense mutation (P(174)L) near the conserved CXXXC motif.
Purpose of the Study:
- To experimentally validate the pathogenic nature of the hSCO1 P(174)L mutation.
- To investigate the functional impact of the P(174)L mutation on COX assembly and activity.
Main Methods:
- Construction of chimeric proteins combining yeast Sco1p and human hSco1p.
- Complementation assays using yeast sco1 null mutants.
- Assessment of COX assembly and activity in cells expressing chimeric proteins.
Main Results:
- Chimeric proteins containing the hSco1p CXXXC motif could complement yeast sco1 null mutants.
- The introduction of the P(174)L mutation into chimeric proteins severely impaired their function.
- Impaired COX assembly and loss of COX activity were observed in the presence of the P(174)L mutation.
Conclusions:
- The P(174)L mutation in hSCO1 is pathogenic, leading to severe functional impairment.
- This mutation disrupts essential processes for COX assembly and activity.
- Findings provide critical insights into the molecular basis of COX deficiency disorders.
Abstract:
Mutations of the yeast SCO1 gene result in impaired COX assembly. Recently, heterozygous mutations in the human homologue hSCO1 have been reported in infants suffering from neonatal ketoacidotic coma and isolated COX deficiency (Valnot et al., 2000). One of the hSCO1 alleles harboured a frame shift mutation resulting in a premature stop codon, the other a missense mutation leading to a substitution of proline(174) by leucine. This position is next to the essential CXXXC motif, which is conserved in all Sco1p homologues. We used chimeric proteins with the amino-terminal portion derived from yeast Sco1p and carboxy-terminal portion including the CXXXC motif from the human hSco1p to provide experimental evidence for the pathogenic nature of the P(174)L mutation. These chimeras are able to complement yeast sco1 null mutants. Introduction of the P(174)L mutation affects the function of these chimeric proteins severely, as shown by impaired COX assembly and loss of COX activity.