Imido Triphosphates

These compounds (10.117a,b) have important bio functions arising from their resistance to hydrolysis. 

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Fig. 14A-C. Guanosine-nucleotides for biophysical characterizations of Ras proteins A gua-nosinediphosphate with a methylanthraniloylester (in grey) at the 3 -position of the ribose B guanosine-5 -[/3,y-imido]-triphosphate (GppNHp) C guanosine-5 -0-(3-thiotriphosphate)...

It is not the binding of GTP but a slow subsequent conformational alteration that activates the Ga GTP adenylate cyclase complex. This was deduced by study of analogs of GTP, such as guanosine 5 -(P, y-imido) triphosphate (GMP-P-(NH)-P or GppNp), which are... 

A recent example is the substrate analogue thymidine 5 -[a,P-imido]triphosphate [141171-20-2] (TMPNPP) (2) which competitively inhibits the human immunodeficiency virus-1 (HIV-1) reverse transcriptase (HIV-1 RT) with a K value of 2.4 micromolar ( TM) (9). The substrate is thymidine 5 -triphosphate... 

The detailed characterization of the enzyme kinetics of DrrA clearly estab-hshed that Rabl GTP and ATP are the preferred enzyme substrates. The enzymatic parameters were used to conveniently estimate the reaction time for multi-miUigram amounts of homogeneously adenylylated Rabl GTP or the nonhydrolyzable derivative of GTP, Rabl GppNHp (guanosrne-5 -0-[(p,y)-imido] -triphosphate). 

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