摘要：

Poly(A)-poly(U) in the absence of template DNA is a unique reaction catalyzed by the RNA polymerase [EC 2.7:7.6] holoenzyme II of . As one approach to investigating the physiological role of the enzyme, the molecular mechanism of poly(A)-poly(U) was studied. , an inhibitor of the elongation of RNA chains, was shown to inhibit poly(A)-poly(U) , and the inhibition was released by a -resistant mutation on the beta subunit. These observations indicate that the active site for the reaction might be located on the beta subunit. Another antibiotic, , which is known to be a specific inhibitor of the initiation of DNA-dependent RNA , effectively inhibited both initiation and elongation steps in poly(A)-poly(U) . This suggests that the enzyme conformation during the chain elongation reaction might be different in this case from that in DNA-dependent RNA . Analysis of the products formed during the initiation reaction indicated that the rate-determining reaction in poly(A)-poly(U) was the of primers of short chain length, and that holoenzyme I was unable to form the first phosphodiester bond in this reaction. Functional properties of holoenzyme II are discussed in connection with these observations.

展开