Ion binding site

Fig. 13. Location of calcium ion binding site in the Gramicidin A channel —. For comparison, the sodium ion binding site is included...

Calcium ion binding site is 1 to 2 A closer to the aqueous solution and pushed away from the... 

One of the recent crystallographic structures of the full length HHR identifies five well-defined divalent ion binding sites, one of them (the C-site) being located in the catalytic pocket and being suggested to have a direct role in catalysis [127],... 

Figure 1.1 The dopamine transporter terminates the action of released dopamine by transport back into the presynaptic neuron. Dopamine transport occurs with the binding of one molecule of dopamine, one chloride ion, and two sodium ions to the transporter the transporter then translocates from the outside of the neuronal membrane into the inside of the neuron.22 Cocaine appears to bind to the sodium ion binding site. This changes the conformation of the chloride ion binding site thus dopamine transport does not occur. This blockade of dopamine transport potentiates dopaminergic neurotransmission and may be the basis for the rewarding effects of cocaine.

In Chapter 2 we have described the nature and strengths of metal ion binding sites in the equation for complex formation in chemistry... 

An alternative approach is that adopted by Horrocks and co-workers, where the aromatic residues in metal-binding proteins are used as sensitizers. Since the distance between the metal and the donor is effectively fixed, this provides a rigid scaffold for the experiment, and the absence of a directly conjugated pathway between the metals means that Forster (through space) energy transfer can be assumed. The r-6 distance-dependence of this means that the extent of sensitized emission from the lanthanide ion provides information on the spatial relationship between the metal-ion binding site (lanthanide ions often bind at Ca2+ sites) and nearby aromatic residues. 58-60... 

The availability of different metal ion binding sites in 9-substituted purine and pyrimidine nucleobases and their model compounds has been recently reviewed by Lippert [7]. The distribution of metal ions between various donor atoms depends on the basicity of the donor atom, steric factors, interligand interactions, and on the nature of the metal. Under appropriate reaction conditions most of the heteroatoms in purine and pyrimidine moieties are capable of binding Pt(II) or Pt(IV) [7]. In addition, platinum binding also to the carbon atoms (e.g. to C5 in 1,3-dimethyluracil) has been established [22]. However, the strong preference of platinum coordination to the N7 and N1 sites in purine bases and to the N3 site in pyrimidine bases cannot completely be explained by the negative molecular electrostatic potential associated with these sites [23], Other factors, such as kinetics of various binding modes and steric factors, appear to play an important role in the complexation reactions of platinum compounds. 

Glutamate and sodium/lithium-induced conformational changes in the GLT-1 transporter have been detected by the altered accessibility of trypsin-sensitive sites to the protease (59). These experiments in GLT-1 shows that lithium can occupy at least one of the sodium ion binding sites, but lithium by itself cannot support coupled transport (59). Therefore, at least one of the sodium binding sites in GLT-1 discriminates between sodium and lithium. As described earlier, this contrasts with EAAC-1, where lithium is able to support uptake. It should therefore be possible to identify residues that are responsible for the sodium/lithium selectivity difference between EAAC-1 and GLT-1. 

Zarbiv, R., Grunewald, M Kavanaugh, M. P., and Kanner, B. I. (1998) Cysteine scanning of the surroundings of an alkali-ion binding site of the glutamate transporter GLT-1 reveals a conformationally sensitive residue. J. Biol. Chem. 273,14231-14237. 

Voss, J., Hubbell, W. L., and Kaback, H. R. (1995) Distance determination in proteins using designed metal ion binding sites and site-directed spin labeling application to the lactose permease of Escherichia coli. Proc. Natl. Acad. Sci. USA 92, 12300-12303. 

Sheikh, S. P, Zvyaga, T. A., Lichtarge, O., Sakmar, T. P., and Bourne, H. R. (1996) Rhodopsin activation blocked by metal-ion-binding sites linking transmembrane helices C and F. Nature 383, 347-350. 

Figure 3.5 Structure (a), porphyrin (b) and metal ion-binding sites (c) in Bacillus subtilis fer-rochelatase. In (c) the two metal ions are a Zn2+ ion (grey) and a fully hydrated Mg2+ ion. The side chains of Glu272, Asp 268 and Glu264 are aligned along a tr-helix (green). (From Al-Karadaghi et al., 2006. Copyright 2006, with permission from Elsevier.)...

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