[ATP analogs in the RNA-polymerase reaction].

The influence of some ATP analogs with the modified ribose residues on the transcription in vitro was studied. It was shown that all analogs are weak inhibitors competing with in RNA synthesis. Under certain conditions (ionic strength = 0.13, 25 degrees C) the only effective inhibitor of RNA synthesis 3'-O-methyl-ATP arrests reaction irreversibly. Perhaps as a result of its incorporation into the terminal position of the growing RNA chain. The increase of the temperature and of the ionic strength results in changes of the character of inhibition: 3'-O-methyl-ATP becomes (like other analogues) a reversible competitive inhibitor with a Ki = 4 . 10(-5) M. Some speculations concerning the mechanism of inhibition are discussed.