DNA-dependent RNA polymerase [EC 2.7.7.6] was purified from the thermophile Thermus thermophilus HB8 and some properties were investigated. 1. Two kinds of the enzyme (enzymes A and B) were found and separated from each other by phosphocellulose column chromatography. Enzyme A could utilize various DNA's as templates, while enzyme B was active only when alternating copolymer of deoxyadenylic and deoxythymidylic acids (poly d(A-T)) was used as a template. The specific activities of enzymes A and B at 65° were 30,000 and 16,000, respectively, which are markedly higher than the value obtained with E. coli enzyme. 2. The enzyme A was extremely thermostable. The activity did not decrease even after incubation for 3 hr at 70°. The maximal rate of RNA synthesis was found at 70°. 3. Both polymerases were resistant to rifampicin but were markedly sensitive to streptolydigin. 4. Four kinds of subunits were found in the enzymes by sodium dodecylsulfate (SDS)- gel electrophoresis; subunit I (M.W. 42,000), II (M.W. 58,000), III (M.W. 140,000), and IV (M.W. 180,000). The subunit compositions of enzymes A and B were 2I-II-III-IV and 2I-III-IV, respectively. A part of enzyme B contained 1 mole of extra polypeptide (named X) of molecular weight 100,000.
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Date et al. (1975) studied this question.