Discriminating between negative cooperativity and ligand binding to independent sites using pre-equilibrium properties of binding curves

ALEJANDRA C VENTURA; FEDERICO SEVLEVER; JUAN PABLO DI BELLA

Buenos Aires

Conferencia; 27th IUPAP International Conference on Statistical Physics, StatPhys27; 2019

IUPAP C3 Commission, Statistical Physics

Negativecooperativity is a phenomenon in which the binding of a first ligand orsubstrate molecule decreases the rate of subsequent binding. This definition isnot exclusive to ligand-receptor binding, it holds whenever two or moremolecules undergo two successive binding events. Negative cooperativity turnsthe binding curve more graded and cannot be distinguished from two independentand different binding events based on equilibrium measurements only. The needof kinetic data for this purpose was already reported. Here, we study thebinding response as a function of the amount of ligand, at different times,from very early times since ligand is added and until equilibrium is reached.Over those binding curves measured at different times, we compute the dynamicrange: the fold change required in input to elicit a changefrom 10 to 90% of maximum output, finding that it evolves in time differentlyand controlled by different parameters in the two situations that are identicalin equilibrium. Deciphering which is the microscopic model that leads to agiven binding curve adds understanding on the molecular mechanisms at play, andthus, is a valuable tool. The methods developed in this article were testedboth with simulated and experimental data, showing to be robust to noise andexperimental constraints.