Derivatives of Guanosine Triphosphate with Ribose 2′‐Hydroxyl Substituents

This report describes the preparation of four methylated and phosphorylated derivatives of GTP, 2′‐O‐methylguanosine 5′‐triphosphate (PPP‐Me 2′ Guo), guanosine 2′‐monophosphate 5′‐triphosphate (PPP‐Guo‐2′P), 3′‐O‐methylguanosine 5′‐triphosphate (PPP‐Me 3 Guo), and guanosine 3′‐monophosphate 5′‐triphosphate (PPP‐Guo‐3′P) These compounds were compared to GTP in their ability to support reactions catalyzed by Escherichia coli initiation factor 2 (IF‐2), elongation factor Tu (EF‐Tu), and elongation factor G (EF‐G). As with previously studied GTI analogues, the nucleotide specificities of IF‐2‐dependent N‐formylmethionylpuromycin formation and EF‐Tu‐dependent Ac‐Phe 2 ‐tRNA formation were similar. There was little difference between the reactions supported by GTP, PPP‐Me 2′ Guo, PPP‐Me 3′ Guo, and PPP‐Guo‐3′P, but PPP‐Guo‐2′P was a poor substrate with both enzymes. A spectrum of activity was observed in EF‐G‐dependent formation of N‐acetylphenylalanyl‐phenylalanylpuromycin. While PPP‐Me 2′ Guo was almost as effective as GTP in supporting translocation. PPP‐Guo‐2′P was a very poor substrate, having even less activity than guanosine 3′‐di‐phosphate 5′‐triphosphate. Intermediate activities were observed with PPP‐Me 3′ Guo and PPP‐Guo‐3′P, the former nucleotide being more active than the latter.