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The bovine lung 20S proteasome binding to reversible inhibitors: modulation by sodium ion
Anna Maria Eleuteri1, Mauro Angeletti
1Post-Graduate School in Clinical Biochemistry, Department of Molecular, Cellular and Animal Biology, University of Camerino, 62032 (MC), Camerino, Italy. annamaria.eleuteri@unicam.it <annamaria.eleuteri@unicam.it>
Abstract:
The effect of sodium ion on the inhibition exerted by Cbz-Leu-Leu-Leu-CHO on the chymotrypsin-like activity of the 20S proteasome isolated from bovine lung was investigated. The experimental data were analyzed using a standard linkage formalism. The calculated equilibrium affinity constants for the sodium ion binding to the free-enzyme and the inhibitor-bound enzyme are compatible to other well-characterized ion-involving heterotropic systems. The functional interdependence between the binding events played by the inhibitor and the sodium ion conforms to a heterotropic modulatory mechanism.