RNA polymerase. Synthesis and kinetic inhibition by 9-(3'-azido-3'-deoxy-beta-D-xylofuranosyl) derivatives of 5'-ATP and 5'-GTP.

The 9-(3'-azido-3'-deoxy-beta-D-xylofuranosyl) nucleoside 5'-triphosphate derivatives of adenine (3'-azido, x-dATP) and guanine (3'-azido, x-dGTP) were prepared by chemical phosphorylation of the corresponding nucleosides. The compounds were characterized by 31P and 1H NMR, high performance liquid chromatography, IR, and TLC. The compounds were examined kinetically and observed to be linear mixed inhibitors for the DNA-dependent RNA polymerase of Escherichia coli (EC 2.7.7.6); Ki values for the 3'-azido, x-dATP and 3'-azido, x-dGTP compounds are 33 and 0.95 microM, respectively. Neither compound functions as an alternate substrate or as a chain terminator during the normal kinetic time course. The 3'-azido, x-dGTP does exhibit a slow time-dependent irreversible inhibition and may therefore function as an alternate substrate and chain terminator with prolonged incubation. Both compounds (3'-azido, x-dATP and 3'-azido, x-dGTP) are photolabile and will derivatize lysine in a coupled photolytic reaction.