Guanosine transporter

Hydrophobized nucleosides form complementary pairs in micelles (Nowick and Chen, 1992 Nowick et al., 1993) and have been used as selective transport systems (Tips) for complementary water-soluble nucleosides through chloroform. A- and U-Tips, for example, have no effect on guanosine transport, whereas G-Tips have an enhancement effect of about 100 and C-Tips of more than 1000. In SDS micelles one finds a 1 1 pair formation of hydrophobized T and A derivatives (Fig. 8.6.7) (Furutaet al., 1991). 

Carter NS, Drew ME, Sanchez M et al. Cloning of a novel inosine-guanosine transporter gene from Leishmanla donovani by functional rescue of a transport-deficient mutant. J Biol Chem 2000 275 20935-20941. 

Arastu-Kapur S, Ford E, Ullman B et al. Functional analysis of an inosine-guanosine transporter from Leishmania donovani The role of conserved residues, asparute 389 and arginine 393. J Biol Chem 2003 278(35) 33327-33333. 

Arastu-Kapur S, Arendt CS, Purnat T et al. Second-site suppression of a nonfunctional mutation within the Leishmania donovani inosine-guanosine transporter. J Biol Chem 2005 280(3) 2213-2219. 

Cyclic Adenosine Monophosphate Table Appendix Membrane Transport Proteins Cyclic Guanosine Monophosphate Non-Selective Cation Channels... 

G proteins comprise several families of diverse cellular proteins that subserve an equally diverse array of cellular functions. These proteins derive their name from the fact that they bind the guanine nucleotides guanosine triphosphate (GTP) and guanosine diphosphate (GDP) and possess intrinsic GTPase activity. G proteins play a central role in signal transduction as well as in a myriad of cellular processes, including membrane vesicle transport,... 

DAT dopamine transporter GDNF glial-derived neurotrophic factor guanosine 5 diphosphate... 

EAAT excitatory amino acid transporter GLUT glucose transporter guanosine 5 -monophosphate... 

Differential pulse voltammetry and electrochemical impedance have demonstrated that G, A, guanosine, and their oxidation products are electrostatically adsorbed on GC and GC(ox) surfaces [47,49]. The strength of adsorption of the DNA bases on the GC surface were found to be similar [49]. Strongly adsorbed G dimers were formed on GC between G and the adsorbed G oxidation products, which slowly cover and block the surface. The appHcation of ultrasound led to removal of the adsorbed species. The effect of this was mainly to enhance transport of electroactive species and to clean the electrode in situ, avoiding electrode fouling. 

Leukocyte Adhesion Deficiency Type 2. Patients with this condition have a defect in the transport or production of the carrier molecule for the carbohydrate L-fucose (guanosine disphosphate L-fucose). The lack of fucose affects the ability of neutrophils to interact with ligands on endothelial cells such as P-selectins and E-selectins (81). Patients are susceptible to recurrent infections similar to those afflicting patients with type 1 leukocyte adhesion deficiency, have periodontal problems, and, in addition, may exhibit growth retardation and neurologic defects. Treatment with oral fucose has been known to be effective in reducing the frequency of infections (80). 

Defect in transport or production of guanosine diphosphate L-fucose. Without the carbohydrate L-fucose, interaction of neutrophils with P- and E-selectins on endofiielial cells is affected. 

Absorption of purines and pyrimidines by cestodes occurs by a combination of passive diffusion and mediated transport. In H. diminuta, purine and pyrimidine uptake is very complex and seems to involve at least three carrier systems (Table 6.9), two of which appear to bind several substrate molecules simultaneously (631). Pyrimidine transport was thought to involve allosteric regulation because the relation between initial uptake and substrate concentration was sigmoidal. However, more recent work (890) has indicated that the sigmoidal kinetics of pyrimidine transport in H. diminuta is an isotope effect, obtained only when 2-14C-labelled pyrimidines were used absorption kinetics of methyl-l4C- and 3H-labelled pyrimidines were hyperbolic. Nucleosides (thymidine, uridine, adenosine and guanosine) are absorbed by H. diminuta, H. citelli and H. microstoma via a specific sodium-dependent, mediated system involving at least two carriers (347). Interestingly, the mechanism displays a diurnal periodicity in H. diminuta (616, 617). 

---