Binding cooperative processes

Mg11 competes only for the B sites. Binding of metal ions to the apoenzyme appears to be a cooperative process involving conformation changes. Metal ions bound at the C sites dialyze readily without detectable change on the structure and function of the enzyme. 

Accumulation of potassium within the cell by a cooperative process is a transmembrane event. However, there is also good evidence that movement of potassium ions through membrane channels is modulated by the binding of calcium ions at channel sites - the "plug in the bath" model (7). Membrane surface glycoproteins with polyanionic terminal strands offer a broad and powerful substrate for these cationic interactions. Competition between hydrogen and calcium ions at these sites has been modeled as the initial transductive step in excitation (8). 

Receptor-ligand binding on a membrane surface in general is usually a highly cooperative process. A possible bilayer conformation mechanism due to the presence of sugar groups will be considered here. 

The other approach to the study of the proteins hydrophobicity by means of free probes is based on the assumption that the process of binding of a probe molecule to a nonpolar site in a given macromolecule can be regarded as transfer of the probe molecule from an aqueous medium to a hydrophobic one 88). Actually the probe-protein binding is usually a cooperative process limited by the type and dimensions of the probe-binding sites 88,89). 

The binding of actinomycin D to calf thymus DNA (0.01M, 0.1M, and 0.2M NaCl) and to poly(dGdC) poly(dGdC) (0.1M NaCl) (Figure 4) was also examined by phase partition techniques. For both DNAs, a cooperative process was seen. In the case of calf thymus DNA, the decreasing salt concentration appears to Increase the degree of cooperativity. 

For a positively cooperative process (i.e., binding of ligands enhances further binding), nH> 1, while for a negatively cooperative process (i.e., binding of ligands inhibits further binding) nH< 1-... 

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