Synthesis and properties of nucleoside 5'-phosphoazidates derived from guanosine and adenosine nucleotides: effective on elongation factors G and Tu dependent reactions.

A new type of nucleoside poly (5'-phosphate) analogue, nucleoside 5"-phosphoazidate, with an azido group on the terminal phosphate of GTP, ATP, GDP, GMP, AND AMP, has been synthesized by nucleophilic displacement of the corresponding activated nucleosides by azide ion in yields of 25-45%. Guanosine 5-phosphoazidates is readily photolyzed by ultraviolet light; the corresponding adenosine derivative photolyzes more slowly. Guanosine 5'-O-(2-azidodiphosphate) and guanosine 5"-O-(3-azidotrophosphate) are competitive inhibitors of the formation of the ribosome-EF-G-GDP-fusidic acid complex and of the ribosome-EF-G GTPase. The dissociation constants of the former reaction are calculated to be 27 and 7 micrometer, respectively, or 270 and 73 times that of GDP. In the latter reaction, which is conducted in the absence of fusidic acid, the Ki values are 330 and 28 micrometer, respectively, or 12 and 1 times that of GDP. Guanosine 5"-O-(2-azidodiphosphate) and guanosine 5'-O-(3-azidotriphosphate) also complete with GTP in the formation of the binary complex. EF-Tu-GTP, with respective Kd values of 750 and 75 relative to GTP.