Expression and characterization of a human pyruvate carboxylase variant by retroviral gene transfer.
Type A pyruvate carboxylase (PC) deficiency presents mainly in the Amerindian population, specifically the Ojibwa, Cree and Micmac tribes of the Algonquin-speaking peoples. The gene for PC contains a homozygous founder mutation (G1828-->A) that results in an Ala610-->Thr amino acid substitution in Ojibwa with Type A PC deficiency. The mutation is located in the highly conserved pyruvate-binding domain of PC. The present paper describes a retroviral expression system for human PC used to analyse the effects of this mutation. We show, through immunoblot analysis, PC enzyme activity assays, reverse-transcription PCR and mitochondrial-import experiments, that this mutation is disease-causing in the Ojibwa population owing to its decreased catalytic activity, decreased steady-state levels of expression and inefficient import into the mitochondria. Our data suggest that this mutation may affect the stability of the protein, resulting in decreased steady-state levels of expression, and that it may also affect the secondary structure of the protein during the import process, thereby inhibiting proper translocation into the mitochondria, where PC is active.
Carbone
Mary Anna
MA
Research Institute, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada M5G 1X8.
Robinson
Brian H
BH
D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D018014:Gene Transfer Techniques; D006801:Humans; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D011766:Pyruvate Carboxylase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D017931:DNA Primers; D011766:Pyruvate Carboxylase