Models for Cooperative Mechanism in Proteins Composed of Subunits

概要

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The cooperative behaviour in the binding of ligands to a protein composed of subunits is studied by using the grand partition function of the system consisting of a protein, ligands and effectors. Each subunit is assumed to be able to change between two conformations with different affinities and interaction between subunits is treated by the nearest-neighbour approximation. It is shown that various models proposed previously by many authors are just the special cases of our present model. Here two kinds of interacting systems, that is, those of the occupational interaction and the conformational interaction are investigated. For these two kinds of interacting systems, i) the deviations of the ligand occupation curve and the conformation curve as functions of ligand concentration from those of the non-interacting system, ii) the rate of conformational change, that is, the ratio of the conformational change at a given ligand concentration to the complete conformational change and iii) the effects of the effector on these properties are investigated. As a result, the way to decide which kind of model is appropriate to explain the mechanisms of cooperativity of our system is proposed.
理論物理学刊行会の論文
1973-05-25