[Topography of cysteine residues in DNA-dependent RNA-polymerase]

Chemical modification of DNA-dependent RNA polymerase with monoiod-[14C]acetic acid and N-[14C]ethylmaleimide has been carried out and position of superficial and functionally important as well as enzymatically non-significant, exposed cysteine residues have been localised in the enzyme. Topography of cysteine residues in the RNA-polymerase alpha-subunit is thoroughly studied. The results are summarized in a model.