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

ALEJANDRA C VENTURA

Buenos Aires

Seminario; Seminarios IFIByNE; 2021

Negative cooperativity is a phenomenon in whichthe binding of a first ligand or substrate molecule decreases the rate ofsubsequent binding. This definition is not exclusive to ligand-receptorbinding, it holds whenever two or more molecules undergo two successive bindingevents. Negative cooperativity turns the binding curve more graded and cannotbe distinguished from two independent and different binding events based onequilibrium measurements only. The need of kinetic data for this purpose wasalready reported. Here, we study the binding response as a function of theamount of ligand, at different times, from very early times since ligand isadded and until equilibrium is reached. Over those binding curves measured atdifferent times, we compute the dynamic range: the fold change required ininput to elicit a change from 10 to 90% of maximum output, finding that itevolves in time differently and controlled by different parameters in the twosituations that are identical in equilibrium. Deciphering which is themicroscopic model that leads to a given binding curve adds understanding on themolecular mechanisms at play, and thus, is a valuable tool. The methodsdeveloped in this article were tested both with simulated and experimentaldata, showing to be robust to noise and experimental constraints.