Divalent cation binding

It has been established by substitution of for Mg that, prior to phosphorylation, the divalent cation binds at a cytosolic site with a stoichiometry of about 1 mol per phosphorylation site [124,125]. These experiments also demonstrated that the phosphorylation rate is sensitive to the nature of the divalent cation bound. With Mg bound, the phosphorylation rate is about 20 times faster than with Ca bound. The divalent cation dissociates after dephosphorylation, suggesting that it is tightly bound to the phosphoenzyme during the reaction cycle. It was also demonstrated that the type of divalent cation that occupies the divalent cation site required for phosphorylation is important for the step 2K E2-P to 2K E2 P to 2K E2 [124,125]. With Mg bound, the 2K E2-P conformer is -sensitive, whereas with Ca bound, the intermediate is -insensitive. 

Bukhman, Y. V., and Draper, D. E. (1997). Affinities and selectivities of divalent cation binding sites within an RNA tertiary structure. J. Mol. Biol. 273, 1020—1031. 

Michishita, M., Videm, V., and Arnaout, M. A. (1993). A novel divalent cation-binding site in the A domain of the /32 integrin CR3 (CDllb/CD18) is essential for ligand binding. Cell 72, 857-867. 

P. Irwin, M. Sevilla and J. Shieh., ESR Evidence for Sequential Divalent Cation Binding in Higher Plant Cell Walls. Biochim. Biophys. Acta 805 (1984) 186. 

Senior, A, h, Richardson, L- V Baker, K.,and Wise, J. 0. (1980), Tight divalent cation-binding sites of soluble adenosine triphosphatase (FI) from beef heart mitochondria and Escherichia coii. J. BieJ. Chem. 255, 7211-7217. 

The conserved sequences and available X-ray crystal structures of C-type lectin CRDs correlate with a common structural motif identified in rat serum mannose-binding protein-A (MBP-A) as represented in O Fig. 2 [19,20]. There are two a-helices, 6 /3-strands, and 2 disulfide bonds common to this motif. Divalent cation binding sites are located in the loop regions. 

The mechanism whereby neomycin B inhibits ribozyme fimction has yet to be elucidated. However, existing results [156] suggest a competitive inhibition of this catalytic RNA by neomycin B, implying that this antibiotic inhibits HDV ribozyme cleavage by disruption of the divalent cationic binding near the catalytic core of the ribozyme. 

Basic proteins elude from HA either with solutions of 0.1 to 0.3 M of univalent cations (anion CF, F, SCN, or phosphate) or with low concentrations (1 to 3 mM) of divalent cations (Ca, Mg +). In the first case, HA works like a cation exchanger. In the second case, the divalent cations bind to the negative phosphate of HA, edging out the amino groups of the proteins in the process. 

The a-subunits display sequence homology of 25-45%, but their seconda and tertiary structures are highly conserved. They all possess the same pattern of residues, a repeated (3 or 4 times) divalent cation-binding motif, and a relatively well conserved transmembrane domain. 

Davey CA and Richmond TJ (2002) DNA-dependent divalent cation binding in the nucleosome core particle. Proceedings of the National Academy of Sciences of the United States of America 99 11169-11174. 

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