Characterization of a plant mitochondrial active chromosome

A method is presented for the partial purification of a plant mitochondrial active chromosome (MAC). This method is based on the presence of the mitoc hondrial chromosome in the insoluble mitochondrial fraction which allows fo r its rapid purification from the bulk of detergent-solubilized proteins by ultra-centrifugation. The resuspended MAC carrying DNA and RNA-binding pro teins retains DNA synthesis and transcription activities comparable to the ones found in isolated mitochondria. In comparison, tRNA-nucleotidyl termin al transferase taken as an example of RNA modifying activities remains in t he soluble fraction. MAC purification is proposed as a rapid and efficient first step in the purification of DNA-binding proteins involved in DNA repl ication and transcription. (C) 1999 Federation of European Biochemical Soci eties.