The multisubunit chloroplast RNA polymerase A from mustard (Sinapis alba L.). Integration of a prokaryotic core into a larger complex with organelle-specific functions

Eur J Biochem. 2000 Jan;267(1):253-61. doi: 10.1046/j.1432-1327.2000.00991.x.


We previously identified two multisubunit plastid RNA polymerases termed A and B. The B enzyme has a bacterial-type polypeptide composition and is sensitive to the prokaryotic transcription inhibitor rifampicin (Rif); the A enzyme has a more complex subunit structure and is Rif-resistant. Here we report results of N-terminal sequencing and MS carried out with the A enzyme, which establish that the latter contains rpo gene products and is structurally related to the B enzyme. Furthermore, evidence is provided that the A enzyme can be converted into a Rif-sensitive enzyme form in a phosphorylation-dependent manner in vitro by a treatment that results in depletion of a beta-like subunit. Database searches using sequence information derived from additional polypeptides that are present in purified A preparations revealed sequence similarity with chloroplast proteins involved in RNA processing and redox control. This proteomics approach thus points to the complexity of the chloroplast transcription apparatus and its interconnections with post-transcriptional and signalling mechanisms.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkaline Phosphatase / metabolism
  • Amino Acid Sequence
  • Chloroplasts / enzymology*
  • Chloroplasts / genetics
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Genes, Plant / genetics
  • Molecular Sequence Data
  • Molecular Weight
  • Mustard Plant / cytology
  • Mustard Plant / enzymology*
  • Mustard Plant / genetics
  • Peptides / chemistry
  • Peptides / genetics
  • Peptides / isolation & purification
  • Phosphorylation
  • Plants, Medicinal*
  • RNA Polymerase I / antagonists & inhibitors
  • RNA Polymerase I / chemistry*
  • RNA Polymerase I / genetics
  • RNA Polymerase I / metabolism*
  • RNA Polymerase II / chemistry
  • RNA Polymerase II / genetics
  • Rifampin / pharmacology
  • Sequence Alignment
  • Sequence Analysis, Protein
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Superoxide Dismutase / chemistry


  • Peptides
  • Superoxide Dismutase
  • Cyclic AMP-Dependent Protein Kinases
  • RNA Polymerase II
  • RNA Polymerase I
  • Alkaline Phosphatase
  • Rifampin