The P(174)L mutation in the human hSCO1 gene affects the assembly of cytochrome c oxidase

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 deficien cy (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 nex t to the essential CXXXC motif, which is conserved in all Sco1p homologues. We used chimeric proteins with the amino-terminal portion derived from yea st Sco1p and carboxy-terminal portion including the CXXXC motif from the hu man hSco1p to provide experimental evidence for the pathogenic nature of th e P(174)L mutation. These chimeras are able to complement yeast sco1 null m utants. Introduction of the P(174)L mutation affects the function of these chimeric proteins severely, as shown by impaired COX assembly and loss of C OX activity. (C) 2000 Academic Press.