Multi-site binding

Competition binding analysis of a variety of phosphopeptides derived from different Cdc4 substrates revealed a range of affinities. For example. Sic IP = 24 pM, FarlP = 2.7 pM, Gcn4 = 0.8 pM. Importantly, multi-site phosphorylation dependent interactions with Cdc4 can be recapitulated with synthetic concatamers of low affinity CPD sites based on either the regions T45 or S76 sites in Sicl. 

To overcome the intrinsic limitation of the pseudoreceptor built on the basis of paclitaxel binding site, a 5D-QSAR [83] model was built, further suggesting a preference for the P-subunit binding site. Results suggest that a multi-site binding is possible, indicating that laulimalide and peloruside can secondarily bind the paclitaxel binding site. 

Detailed kinetics of ATP hydrolysis in single-site (uni-site) and steady-state (multi-site) conditions by beef heart Fi were studied extensively (Fig. 11.5).45 46) At an ATP/ Fi ratio of less than 1, ATP binds to a catalytic site and is hydrolyzed slowly (uni-site catalysis). The equilibrium constant between bound substrate (ATP) and products (ADP and Pi) bound at the catalytic site of Fi was close to 1, indicating that the equilibrium can occur without change in free energy. In the presence of excess ATP (multi-site catalysis), ATP binds to all three catalytic sites, and the ATP at the first site is hydrolyzed at a rate that is at least 106 times higher than is the case in uni-site catalysis. 

Fig. 3.3 The raw data output of ITC is transformed to show the heat exchange at each injection (kcal mol of injectant), obtained by integration of the area of each spike in the raw data output, as a function of the molar ratio of the protein-ligand binding interaction. The curve is then computer-generated as the best fit to either a one-site or multi-site binding model.

Consequently, the amount of bound water (per volume unit) interacting with the IgG molecules is lower than that with BSA. Therefore, C (T) curve for SCN-IgG system lies below C (T) curve for SCN-BSA (Figure 6.55). Covalent binding results in a multi-site attachment of IgG to the carbon surface via CMC-activated surface groups, which is more significant than cross-linking of the protein in the solution. It leads to the displacement of a fraction of adsorbed water by IgG (and reduction of... 

Chapter 28. Multi-site Cooperative Ligand Binding... 

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