Separation and Characterization of the Subunits of Ribonucleic Acid Polymerase

Abstract

Abstract This paper presents studies on the subunit structure of Escherichia coli DNA-dependent RNA polymerase. Phosphocellulose column purified enzyme is denatured and its polypeptide chains separated by gel filtration on Sephadex G-200 in the presence of 1% sodium dodecyl sulfate. The amino acid compositions, molecular weights, NH2 terminal amino acids, and molar ratios of these polypeptide chains are presented. It is concluded that phosphocellulose enzyme has the structure α2ββ' where the molecular weights of the chains α, β, and β' are 39,000 ± 5%, 155,000 ± 10%, and 165,000 ± 10%, respectively. In addition, a small protein component, ω, with molecular weight of 9,000 ± 10% is observed. These subunits are not joined together by disulfide linkages. From these data one can compute a molecular weight of 400,000 ± 10% for the monomeric form of the phosphocellulose purified polymerase.