Calcium site specificity

Lacaz-Vieira, F. (1997). "Calcium site specificity. Early Ca2+-related tight junction events." J Gen Physiol, 110(6), 727-40. 

Tsuji, F. I., Inouye, S., Goto, T., and Sakaki, Y. (1986). Site-specific mutagenesis of the calcium-binding photoprotein aequorin. Proc. Natl. Acad. Sci. USA 83 8107-8111. 

In contradistinction to site-specific molecules there are other toxins which, in a sense, create their own specificity. Thus ionophore toxins, by opening up the cell membrane to sodium and calcium ions, create their own specificity. Prime examples of this are found in cytolytic toxins in general, and jellyfish toxins and palytoxin in particular. 

Among the oldest women with impaired calcium balance a high caffeine intake may predispose to cortical bone loss. However, effects were age and site specific and after... 

Johnson, J.D., Collins, J.H., and Potter, J.D. (1978) Dansylaziridine labeled troponin C. A fluorescent probe of calcium ion binding to the calcium ion-specific regulatory sites./. Biol. Chem. 253, 6451. 

Snyder, E. E., Buoscio, B. W., and Falke, J. J. (1990). Calcium(II) site specificity Effect of size and charge on metal ion binding to an EF-hand-like site. Biochemistry 29, 3937-3943. 

Narhi et al. (1991) recently reported an enhancement in the thermal stability of aprA-subtilisin by three point mutations. The mutations were ASNi. SER and ASN. SER to prevent cyclisation with the adjacent glycines and ASN . ASP in the Ca binding loop. The mutant form also exhibits improved stability to detergent denaturation with little dependence on calcium concentration. Subtilisin 8350 (derived from subtilisin BPN via six site-specific mutations) was found to be 100 times more stable than the wild type enzyme in aqueous solution and 50 times more stable than the wild type in anhydrous dimethylformamide (Wong et al, 1990)... 

The calcium sites in troponin C have been studied by X-ray absorption near edge structure (XANES).244 In all four cases, Ca2+ appears to be coordinated to carboxylate and carbonyl groups, and no structural differences could be found between the two classes of sites. Binding of Mg2+ causes a distortion of the geometry of the calcium site. Thus, the reduced affinity for Ca2+ of the Ca2+-Mg2+ sites in the presence of Mg2+ may not simply be due to competition with Mg2+, but due to some conformational change induced at these sites by Mg2+. The similarity of all four Ca2+ sites means that local bonding effects do not explain the inability of Mg2+ to bind to the calcium-specific sites I and II. The XANES of parvalbumin differs from that of troponin C. 

Wield R, Franz C, Scholl FA, Heizmann CW, Schafer BW. 1997. Repression of the candidate tumor suppressor gene S100A2 in breast cancer is mediated by site-specific hypermethylation. Cell Calcium 22(4) 243-254. 

Pillay V, Fassihi R. In vitro release modulation from cross-linked pellets for site-specific drug delivery to the gastrointestinal tract. Part 2. Physicochemical characterization of calcium-alginate, calcium-pectinate and calcium-alginate-pectinate pellets. / Control Release 1999 59 243-256. 

Once released within the lung, the leukotrienes are hypothesized to induce bronchoconstriction of airway smooth muscle through a receptor-mediated process, Binding sites specific for the leukotrienes have been identified in human lung parenchyma (Nicosia et al., 1984) and are believed to represent receptors on the plasma membrane of airway smooth-muscle cells. The interaction of the leukotrienes with a receptor is then hypothesized to induce the release of intracellular calcium in the smooth-muscle cell (Welchman et al., 1983). As with mast cells, intracellular events within the smooth-muscle cells are believed to be modulated via the calcium-binding protein... 

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