Detection of three DNA-binding proteins from lupine mitochondrial

To investigate the mechanism of transcription in plant mitochondria, proteins displaying binding activity to mitochondrial plasmid promoters were studied. We have identified a conserved nonanucleotide motif at the 5' end of a Lupinus albus mitochondrial plasmid transcript. Three proteins with molecular masses of ca. 25, 30, and 48 kD interacted with ds oligonucleotides, representing different parts of the plasmid promoter. Proteins with molecular masses 25 and 30 kD seem to represent two components of a heterodimer. The DNA-binding activities of these proteins have been confirmed by electrophoretical mobility shift assay (EMSA), SDS-PAGE, Southwestern, and UV cross-linking assays. The specificity of DNA-binding reaction was examined by competition experiments.