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首页> 外文期刊>Journal of Molecular Biology >A bacterial transcription terminator with inefficient molecular motor action but with a robust transcription termination function.
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A bacterial transcription terminator with inefficient molecular motor action but with a robust transcription termination function.

机译：一种细菌转录终止子，其分子运动功能低下，但具有强大的转录终止功能。

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摘要

Molecular motors such as helicases/translocases are capable of translocating along the single-stranded nucleic acids and unwinding DNA or RNA duplex substrates using the energy derived from their ATPase activity. The bacterial transcription terminator, Rho, is a hexameric helicase and releases RNA from the transcription elongation complexes by an unknown mechanism. It has been proposed, but not directly demonstrated, that kinetic energy obtained from its molecular motor action (helicase/translocase activities) is instrumental in dissociating the transcription elongation complex. Here we report a hexameric Rho analogue (Rv1297, M. tb. Rho) from Mycobacterium tuberculosis having poor RNA-dependent ATP hydrolysis and inefficient DNA-RNA unwinding activities. However, compared to Escherichia coli Rho, it exhibited very robust and earlier transcription termination from the elongation complexes of E. coli RNA polymerase. Bicyclomycin, an inhibitor of ATPase as well as RNA release activities of E. coli Rho, inhibited the ATPase activity of M. tb. Rho with comparable efficiency but was not efficient in inhibiting its transcription termination function. Unlike E. coli Rho, M. tb. Rho was capable of releasing RNA in the presence of nonhydrolyzable analogues of ATP quite efficiently. Also, this termination function most likely does not require NusG, an RNA-release facilitator, as this Rho was incapable of binding to NusG either of M. tb. (Rv0639) or E. coli. These results strongly suggest that the ATPase activity of M. tb. Rho is uncoupled from its transcription termination function and this function may not be dependent on its helicase/translocase activity.
机译：分子驱动器（例如解旋酶/转座酶）能够利用源自其ATPase活性的能量沿着单链核酸转移并解开DNA或RNA双链体底物。细菌转录终止子Rho是六聚解旋酶，通过未知机制从转录延伸复合物中释放RNA。已经提出但没有直接证明，从其分子运动作用获得的动能（解旋酶/转座酶活性）在解离转录延伸复合物中起重要作用。在这里，我们报告了结核分枝杆菌的六聚体Rho类似物（Rv1297，M. tb。Rho），具有差的RNA依赖性ATP水解和无效的DNA-RNA解旋活性。但是，与大肠杆菌Rho相比，它从大肠杆菌RNA聚合酶的延伸复合物中表现出非常强大且更早的转录终止。双环霉素是ATPase的抑制剂，同时也具有大肠杆菌Rho的RNA释放活性，可抑制结核分枝杆菌的ATPase活性。 Rho具有相当的效率，但不能有效抑制其转录终止功能。与大肠杆菌Rho不同，M。tb。 Rho在ATP的不可水解类似物存在下能够有效释放RNA。同样，这种终止功能很可能不需要RNA释放促进剂NusG，因为该Rho无法与结核分枝杆菌的NusG结合。 （Rv0639）或大肠杆菌。这些结果强烈暗示了结核分枝杆菌的ATP酶活性。 Rho与它的转录终止功能脱钩，该功能可能不依赖于其解旋酶/转移酶活性。

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