Studies on a Thermophilic RNA Polymerase which is Active Only on Poly d (A-T) and Poly dAdT
1975 年 78 巻 5 号 p. 955-967
詳細
1975 年 78 巻 5 号 p. 955-967
Two types of RNA polymerases [EC 2. 7. 7. 6], polymerases A and B, exist in thermophilic bacteria, Thermus thermophilus HB8. Polymerase B is apparently like the core enzyme of polymerase A but is active only when an alternating copolymer of deoxyadenylic and deoxythymidylic acids (poly d(A-T)) or a mixture of homopolymers of deoxyadenylic acid and deoxythymidylic acid (poly dAdT) is used as a template. Polymerase B was further characterized to elucidate its relation to polymerase A and to determine why it is inactive on natural DNA's.
1. Polymerase B did not show pyrophosphate exchange activity. Dinucleoside monophosphates did not activate the RNA-synthesizing activity. The results suggested that polymerase B had no initiation and presumably no elongation activities.
2. Polymerase B had about 6 times greater affinity to DNA than polymerase A. The binding of polymerase B to DNA was, however, reversible. The complex of DNA with polymerase A was stable and the polymerase was not removed from the initial complex even when a large amount of DNA was added.
3. E. coli σ subunit could not stimulate the activity of polymerase B toward DNA's.
4. Polymerase B could utilize poly d(A-T) and poly dAdT as templates, but could not use Bacillus cereus DNA, though the structure is reported to be similar to that of poly d(A-T).
