The plastid rpoA gene encoding a protein homologous to the bacterial RNA polymerase alpha subunit is expressed in pea chloroplasts

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Abstract
The gene rpoA, encoding a protein homologous to the alpha subunit of RNA polymerase from Escherichia coli has been located in pea chloroplast DNA downstream of the petD gene for subunit IV of the cytochrome b-f complex. Nucleotide sequence analysis has revealed that rpoA encodes a polypeptide of 334 amino acid residues with a molecular weight of 38916. Northern blot analysis has shown that rpoA is co-transcribed with the gene for ribosomal protein S11. A lacZ-rpoA gene-fusion has been constructed and expressed in E. coli. Antibodies raised against the fusion protein have been employed to demonstrate the synthesis of the rpoA gene product in isolated pea chloroplasts. Western blot analysis using these antibodies and antibodies against the RNA polymerase core enzyme from the cyanobacterium, Anabaena 7120, has revealed the presence of the gene product in a crude RNA polymerase preparation from pea chloroplasts.