Investigating LC8 Cooperativity via Molecular Dynamics

The hub protein LC8, interacts with over 100 binding partners in the cell and participates in a range of cell activities including mitosis and viral interactions. LC8 is a symmetric homodimer with two identical binding grooves that typically bind to intrinsically disordered (ID) regions of client proteins, linking them together. Recent experiments have revealed significant cooperativity in LC8: Isothermal titration calorimetry (ITC) experiments demonstrate a significant change in the affinity of the second binding event - as well as heterogeneous enthalpy/entropy signatures for different peptides. In order to investigate the atomic resolution mechanisms of cooperativity in these systems, we examine multiple LC8 bound to different client peptides in three different binding conditions – apo, singly bound, and doubly bound – using a series of μs-scale molecular dynamics (MD) simulations. We compare dynamics and fluctuations across the different conditions and for peptides with varying binding properties to elucidate the cooperativity signals in these systems and find that local fluctuations support a range of cooperative behaviors among the peptides.