A Mechanism for Adaptative Remodeling in the Bacterial Flagellar Motor

Flagellar motors of Escherichia coli switch stochastically between clockwise (CW) and counter-clockwise (CCW) rotational states, enabling the cell to perform chemotaxis.  CW rotation is promoted by the binding of an activated cytoplasmic response regulator, CheY-P, to a rotor component, FliM. Yuan et al, Nature (2012) recently discovered that the rotor complex undergoes remodeling in response to persistent decline in the levels of CheY-P, a mechanism which may be responsible for countering cell to cell variations in concentrations of chemotactic proteins, as well as aiding in navigating rapidly changing environments. However, the feedback mechanism which controls this remodeling remains a mystery. I will present our latest results which establish a link between adaptative remodeling and the dynamics of the motor, and propose a model mechanism for this adaptation. These results suggest a regulatory role for protein exchange in multi-protein complexes, which could be a tactic employed in other biological machines as well.