KINETIC-ANALYSIS OF GENETIC COMPLEMENTATION IN HETEROKARYONS OF PROPIONYL COA CARBOXYLASE-DEFICIENT HUMAN-FIBROBLASTS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 32  (1) , 16-25
Abstract
Genetic complementation of propionyl CoA carboxylase (PCC) deficiency was studied in cultures of polyethylene glycol (PEG)-induced heterokaryons using mutant fibroblast lines assigned to 5 mutant classes, designated bio, pcc A, pcc B, pcc C and pcc BC. By measuring PCC activity directly in extracts of fused cells or indirectly in intact cells by [1-14C]propionate utilization, the nonlinear nature of the PCC deficiency complementation map described by Gravel et al. was confirmed. When the complementation kinetics were studied, 3 distinct patterns using the [1-14C]propionate utilization assay were detected. When either pcc A or pcc C lines were fused to bio cells, 14C-fixation increased to half of the maximally restored values within 4 h. In pcc A .times. pcc C crosses or in pcc A .times. pcc B crosses, complementation was much slower. In fusions between pcc B and pcc C cells, a 3rd pattern was elicited; complementation was incomplete, maximum restoration of PCC activity being < 20% of that observed in other complementing crosses. The bio and pcc mutations evidently affect different genes. Complementation between pcc A and pcc B, pcc C or pcc BC lines is probably intergenic and involves subunit exchange and synthesis of new PCC molecules. Complementation between pcc B and pcc C mutants is probably interallelic.