GTP Green

Figure 13.8 Interactions involved in the switch from the inactive GDP- (blue) to the active GTP- (green) bound forms of G from transducin. The diagram illustrates the local changes required in the switch I and II regions in order to bring the side chain of Thr 177 and the main chain N of Gly 199 into contact with the 7 phosphate of GTP. (Adapted from D. Lambright et al., Nature 369 621-628, 1994.)...

Fig. 17.18 Characterization of GTP Green (a) absorption spectrum in MeOH (b)excitation and emission spectra in MeOH (c) fluorescence emission spectra (excitation = 480nm)of G49 with 100pM of GTP, ATP, all other 14 analytes and blank control in lOmM HEPES buffer (pH = 7.4) (d) fluorescence emission spectra (excitation 480nm, cutoff 495nm) of G49 with 500, 100, 50, 20, 12, lOpM GTP and blank control in lOmM HEPES buffer (pH = 7.4) (e) binding isotherm from the fluorescence titration experiment with emission at 540nm (f) picture of G49 with analytes under 365 nm UV lamp light...

Based on this unprecedented high selectivity of G49 to GTP and its visual green fluorescence increase, we dubbed this compound GTP Green. This is a clear example that unexpected molecular interactions could happen and be discovered through a diversity-oriented fluorescence library approach, even within two small molecules. 

Figure 6-8 Lead sensor candidates, H22 and GTP Green, for glutathione and GTP, respectively, derived from diversity-directed sensor discovery approaches.

In the initial screen, one compound (given the name GTP Green, Fig. 6-8) displayed fluorescence enhancement ( tum-on ) upon GTP binding and was favorably photostable compared to other candidates [76], Prior to the discovery of GTP Green, the only other GTP sensor (rationally designed) was a turn-off sensor [78], GTP Green displayed a red-shifted 80-fold fluorescence enhancement (Tern = 540 nm) in the presence of GTP and only < two-fold increases with the other nucleotide triphosphates ATP, TTP, and UTP. This compound was also found to be selective for GTP over the mono- and diphosphate homologs. 

Figure 13.4 Schematic diagram (a) and topology diagram (b) of the polypeptide chain of cH-ras p21. The central p sheet of this a/p structure comprises six p strands, five of which are parallel a helices are green, p strands are blue, and the adenine, ribose, and phosphate parts of the GTP analog are blue, green, and ted, respectively. The loop regions that are involved in the activity of this protein are red and labeled Gl-GS. The Gl, G3, and G4 loops have the consensus sequences G-X-X-X-X-G-K-S/T, D-X-X-E, and N-K-X-D, respectively. (Adapted from E.R Pai et al., Nature 341 209-214, 1989.)...

Figure 13.6 Schematic diagram of Go. from transducin with a bound GTP analog. The polypeptide chain is organized Into two domains a catalytic domain (light red) with a structure similar to Ras, and a helical domain (green) which is an Insert in the loop between al and P2. There are three switch regions (violet) that have different conformations in the different catalytic states of Go.. The GTP analog (brown) Is bound to the catalytic domain in a cleft between the two domains. (Adapted from J. Noel et al.. Nature 366 654-663, 1993.)...

FIGURE 12-13 Interaction of Gs with adenylyl cyclase. (PDB ID 1AZS) The soluble catalytic core of the adenylyl cyclase (AC, blue), severed from its membrane anchor, was cocrystallized with G,, (green) to give this crystal structure. The plant terpene forskolin (yellow) is a drug that strongly stimulates the enzyme, and GTP (red) bound to Gsa triggers interaction of Gsa with adenylyl cyclase. 

Fig. 2 Ribbon diagram of the structure of the a/p-tubulin dimer in 2D zinc-induced sheets (PDB entry 1TUB). The p monomer is on top. Some elements involved in PTX binding and lateral contacts are colored M loop in green, S9-S10 loop in blue, helix H7 in yellow, and helix H3 in orange. Small-molecule ligands are represented as sticks PTX in red, GDP and GTP in magenta. The a-tubulin S9-S10 loop occupies a position equivalent to that of PTX in P-tubulin...

Fig. 4 Diagram of the crystal structure of the T2R complex showing the binding sites of MT-destabilizing drugs (PDB entry 1Z2B) [13]. Protein subunits are represented as ribbons. RB3-SLD is colored orange, a-tubulin is purple, and p-tubulin is green. Small-molecule ligands are represented as spheres (vinblastine orange, colchicine red, GTP yellow, and GDP magenta). Colchicine binds to the p-subunit at the intradimer interface. Vinblastine binds at the interdimer interface...

Fig. 4 Left, location of the vinblastine and colchicine binding sites in tubulin (1Z2B structure), a- and (3-tubulin are represented as yellow and magenta ribbons, respectively vinblastine and DAMA-colchicine are represented as green and cyan spheres, respectively GTP and GDP are represented as pink sticks. Vinblastine binds at the interdimer interface, whereas colchicine binds at the intradimer interface. Right, zoom on the vinblastine binding site. Secondary structure elements contacting vinblastine are colored blue...

Guo, Q., Zhao, B., and Li, M. 1996. Studies on protective mechanisms of four components of green tea polyphenols (GTP) against lipid peroxidation in synaptosomes. Biochem. Biophys. Acta 1304 210-22. 

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