Calcium ions binding

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... 

Calcium deposition biology, 6, 597 Calcium ions binding... 

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. 

At 293 K two calcium ions bind cooperatively at the C-domain, with logK = 7.3, 7.6. 

Urry, D. W. Neutral sites for calcium ion binding to elastin and collagen A charge neutralization theory for calcification and its relationship to arteriosclerosis. Proc. Nat Acad. Sci. (Wash.) 68, 810 (1971)... 

Like as2-casein, /e-casein has two disulfide bonds which can form cross-links with /3-lactoglobulin. The N-terminal two-thirds of the molecule is hydrophobic and contains the two disulfide bonds. The C-termi-nal end is hydrophilic, polar, and charged. It varies in the number of attached carbohydrate moieties and has only one phosphate group. These characteristics make /c-casein ideal for the surface of casein micelles, where it is most often found. It is not susceptible to calcium ion binding, as the other caseins are, and when present on the surface of micelles, it protects the other caseins from calcium (McMahon and Brown 1984A Swaisgood 1982). 

The catalytic activity of porcine pancreatic a-amylase, another member of the glucosyl hydrolase family, is metal cofactor-dependent [53]. A calcium ion-binding site is located at the interface of an antiparallel f-sheet, inserted in one of the loop regions of the /ia-barrel, and the core structure. In the calcium-bound state, the insertion stabilizes the substrate-binding site, and indirectly constrains part of the active site in a catalytically competent conformation. 

EF-hand proteins, each EF-hand motif of the penta-EF-hand proteins fhnctions separately withont cooperativity. Even if even-numbered calcium ions are bound, it is not necessary that they are paired. For example, in grancalcin and ALG-2, two calcium ions bind to EF-1 and EF-3 while the paired partners EF-2 and EF-4 are empty. hi24,i2s,i28... 

Figure 18 The structure of the extracellular region of Ep-cadherm (1L3W). Calcium ions bind to the loops between each two adjacent domains and the whole protein in the structure forms a curvature. N-acetyl-D-glucosamine molecules attached to the cadherin surface are in gray...

Coordination chemistry of RE(III) with amino acids has been attracting much interest since the early 1970s after the discovery that certain RE(III) ions could be used as probes of calcium ion binding sites in proteins and enzymes [118, 119], Since then, a large amount of work on the solution and structural chemistry of rare earth-amino acid complexes has been published. The solution studies involve all of the rare earth elements and 13 (Gly, Ala, Val, Leu, Phe, Met, Pro, Ser, Tyr, His, Lys, Trp, and Arg) of the 20 standard amino acids, and more than 100 of the RE(III)-amino acid complexes have been structurally characterized. This section will cover the synthetic, structural, and solution chemistry of these complexes. 

Damall, D.W and Birnbaum, E.R. (1970) Rare earth metal ions as probes of calcium ion binding sites in proteins neodunium(III) acceleration of the activation of trypsinogen. Journal of Biological Chemistry, 245 (23), 6484-6486. 

Deafness occurred after 5 days treatment with dantrolene 25 mg/day in a patient who was also taking long-term baclofen and diazepam (8). This may have been coincidental, but the authors suggested that dantrolene may have caused the effect by interfering with the release of calcium from the sarcoplasmic reticulum. It is therefore interesting that one hypothesis that explains the ototoxicity of aminoglycoside antibiotics involves disturbance of calcium ion binding and phosphorylation processes (SED-11, 549). 

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