Conformational change category listing 3 | Beckstein Lab

The enzyme adenylate kinase (AdK) undergoes a large hinge-like motion. In 2009, we studied the conformational transition between open and closed E. coli AdK without substrate, i.e. “apo AdK”, with a variety of computational methods. As part of the study we also produced a free energy landscape (a potential of mean force or PMF) as a function of the two domain angles. Here we make the data of the underlying free energy landscape available to other researchers so that they can use them in their own research.

While equilibrium MD is considered the most robust approach to simulating macromolecular conformational changes, conformational transitions are rare events that take place on much faster timescales than the waiting times spent in metastable equilibrium states. Equilibrium simulations thus spend relatively little time sampling actual transition events. Fast transition path sampling methods seek to mitigate the rare event sampling problem, though the full extent to which biased or coarse-grained approaches can replicate physical ensembles of transitions is unknown.

We show that one of the best-studied secondary active transporters, the lactose permease LacY, goes through an occluded conformation during its transport cycle. We propose an atomically detailed model of the apo-occluded state. The simulations predict the formation of a transient salt bridge that has been hypothesized in the canonical model for transport of LacY. The simulations are validated by comparison to experimental EPR DEER data, using a new approach to simulate spin-label distance distributions through post-processing of molecular dynamics trajectories. We also define a set of order parameters that consistently classify all known MFS transporter structures as outward-open, occluded, or inward-open conformations.