Synthesis of deoxyguanosine polyphosphates and their interactions with the guanosine 5'-triphosphate requiring protein synthetic enzymes of Escherichia coli.

A chemical synthesis of deoxyguanosine analogs of the guanosine polyphosphates accumulated by bacteria during the stringent response is described. Both deoxyguanosine 3'-diphosphate 5'-triphosphate (d-pppGpp) and deoxyguanosine 3'-diphosphate 5'-diphosphate (d-ppGpp) were prepared, as well as the by-products deoxyguanosine 3'-monophosphate 5'-triphosphate (d-pppGp) and deoxyguanosine 3'-monophosphate 5'-diphosphate. A significant difference between d-(p)ppGpp and guanosine 3'-diphosphate 5'-tri- or 5'-diphosphate (p)ppGpp) is that the 3'-pyrophosphate moiety is alkali stable in the deoxyguanosine and alkali labile in the guanosine polyphosphates. The new GTP analogs d-pppGp and d-pppGpp were compared to GTP, dGTP, and pppGpp in their ability to support reactions catalyzed by the Escherichia coli protein synthetic enzymes initiation factor 2, elongation factor Tu, and elongation factor G (EF-G). Like pppGpp, both d-pppGp and d-pppGpp showed substantial deficiency only in reactions requiring EF-G. While d-pppGpp closely resembled pppGpp in its very low activity with EF-G, d-pppGp was somewhat more active. Nevertheless, d-pppGp was a poor substrate in EF-G-dependent translocation. Qualitatively and quantitatively its support of translocation was very similar to the reaction driven by periodate-oxidized and borohydride-reduced GTP, a derivative of GTP in which the ribose ring has been cleaved between the 2'- and 3'-hydroxyl groups.