Correction of the Metabolic Defect in Propionic Acidemia Fibroblasts by Microinjection of a Full-Length cDNA or RNA Transcript Encoding the Propionyl-CoA Carboxylase β Subunit

Abstract Propionyl-CoA carboxylase (PCC) is a mitochondrial, biotin-dependent enzyme, composed of an equal number of α and β subunits, that, functions in the catabolism of branched-chain amino acids and other metabolites. Mutations of the PCCA (α subunit) or PCCB (β subunit) gene cause the inherited metabolic disease, propionic acidemia. We report the cloning of a full-length cDNA encoding the β subunit of human PCC. The open reading frame encodes a pre-β polypeptide of 539 amino acids (58,205 Da). The cDNA was introduced into the expression vector, pRc/CMV, and microinjected into the nucleus or, as ribotranscripts, into the cytoplasm of fibroblast lines from patients with defects of the β subunit. The restoration of function was monitored by autoradiography of PCC-dependent [ 14 C]-propionate incorporation into cellular protein. These results confirm the completeness of the clone and demonstrate the capacity for β subunits derived from the microinjected cDNA or RNA to be transported into mitochandria and assembled with endogenously derived subunits to form functional PCC.