Speaker
Description
The cooperative binding of molecular agents onto a substrate is pervasive in living systems, particularly stochastic processes inside cells. When the number of binding sites is small enough, we can rely on a fluctuation analysis of the number of substrate-bound units, an experimentally accessible quantity, to study whether a system shows cooperativity.
First, we present a general-purpose grand canonical Hamiltonian description of a small one-dimensional (1D) lattice gas with either nearest-neighbor or long-range interactions as prototypical examples of cooperativity-influenced adsorption processes. We propose 1) a criterion to determine whether a given adsorption system exhibits cooperative or anti-cooperative behavior and 2) a method to quantify the amplitude of the ligand-ligand interaction potential.
Second, we compare the theoretical predictions of our model to bead assay measurements of the bacterial flagellar motors (BFM) of E. coli. In this way, we find evidence that cooperativity controls the mechano-sensitive dynamical assembly of the torque-generating units, the so-called stator units, onto the BFM. Finally, we estimate the stator-stator interaction potential and attempt to quantify the adaptability of the BFM.
References:
1 Franco-Oñate M-J, Parmeggiani A, Dorignac J, Geniet F, Walter J-C, Pedaci F, Nord A L, Palmeri J, Walliser N-O (2023). Signature of (anti)cooperativity in the stochastic fluctuations of small systems: application to the bacterial flagellar motor. [arXiv:2307.00636]
2 Perez-Carrasco R, Franco-Oñate M-J, Walter J-C, Dorignac J, Geniet F, Palmeri J, Parmeggiani A, Walliser N-O, Nord A. (2022). Relaxation time asymmetry in stator dynamics of the bacterial flagellar motor. Science Advances, 8(12), eabl8112, [bioRxiv:451114]
