Guanosine-3 ,5 -tetraphosphate

A guanosine tetraphosphate with pyrophosphate groups in the 3 - and 5 -positions was synthesized by double phosphorylation of the corresponding guanosine 3, 5 -dipho-sphate.1501... 

Guanosine tetraphosphate (ppGpp) concentration under normal conditions, after amino acid starvation, and after readdition of amino acids ( = wild-type cells A = relA cells and = spoT cells). 

GTP is not involved. Guanosine tetraphosphate (ppGpp), which mediates the response, is formed from ATP and GDP by a protein called stringent factor. 

Quite a different form of exopolyphosphatase was purified from the vacuolar sap of S. cerevisie (Andreeva et al., 1998b). Its molecular mass determined by gel filtration was 245 kDa. This exopolyphosphatase hydrolysed PolyP3 only slightly, and its specific activity increased with the increase in PolyP chain length (Table 6.6). It was unable to hydrolyse adenosine- and guanosine-tetraphosphates and was insensitive to antibodies inhibiting the low-molecular-mass exopolyPase of the cytosol (Table 6.4). This enzyme was stimulated by divalent metal cations to a much lesser extent than 40 kDa exopolyphosphatase (Table 6.5) and was inhibited by EDTA (Table 6.4). The inhibitory effect of EDTA is explained by the binding of Co2+, which is the best activator of the vacuolar exopolyphosphatase at 0.1 mM. 

The enzyme splitting both adenosine-tetraphosphate and guanosine-tetraphosphate was purified to homogeneity from yellow lupin seeds (Guranowski et al., 1997). The polypeptide of 25 kDa catalysed the hydrolysis of nucleoside-5 -tetraphosphate to nucleoside triphosphate and P , and hydrolysed PolyP3, but neither pyrophosphate nor PolyPs The divalent carions Mg2+, Co2+, Ni2+ or Mn2+ were required for the reaction. 

T. Nystrom (1994). Role of guanosine tetraphosphate in gene expression and the survival of glucose or seryl-tRNA starved cells of Escherichia coli K-12. Mol. Gen. Genet., 245, 355-362. 

A. L. Svitil, M. Cashel and J. W. Zyskind (1993). Guanosine tetraphosphate inhibits protein synthesis in vivo. A possible protective mechanism for starvation stress in Escherichia coli. J. Biol. Chem., 268, 2307-2311. 

Extra p s can be added to indicate pyrophosphate bonds, e.g. pppGp guanosine tetraphosphate. 

A number of 1 3 C nmr studies on the structure and conformation of nucleotides have been performed in the last few years (Birdsall and Feeney, 1972 Blumenstein and Raftery, 1972, 1973 Tapper et al., 1972, 1973 Lapper and Smith, 1973 Que et al., 1973 Smith et al., 1973a Birdsall et al., 1973a). Guanosine tetraphosphate, a nucleotide which exhibits regulatory control in the interaction of... 

Manoil, C. and Kaiser, D. (1980). Accumulation of guanosine tetraphosphate and guanosine pentaphosphate in Myxococcus xanthus during starvation and myxospore formation. J. Bacteriol. 141, 297-304. 

Neubauer P, Ahman M, Tbmkvist M, Larsson G, and Enfors SO (1995) Response of guanosine tetraphosphate to glucose fluctuations in fed-batch cultivations of Escherichia coli. Journal of Biotechnology 43 195-204. 

Higher polyphosphate derivatives of purine ribonucleosides are known. Adenosine tetraphosphate has been isolated from horse muscle the compound appears to be a 5 -polyphosphate, but the structure of the polyphosphate portion is uncertain and a biological role is unknown (25). Guanosine tetraphosphate and adenosine pentaphosphate have also been reported. 

L-fucose, D-rhamnose GDP-D-mannuronic acid GDP-4-keto-6-deoxy-D-mannose P, P -Diguanosine tetraphosphate P, P -Diguanosine triphosphate Guanosine tetraphosphate Cytidine diphosphate-X CDP-D-glucose CDP-L-ribitol... 

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