Molecular Simulation and Biochemical Studies Support an Elevator-type Transport Mechanism in EIIC

摘要: Enzyme IIC (EIIC) is a membrane-embedded sugar transport protein that part of the phosphoenolpyruvate-dependent phosphotransferases. Crystal structures two members glucose EIIC superfamily, bcChbC in inward-facing conformation and bcMalT outward-facing conformation, were previously solved. Comparing led us to hypothesis translocation could be achieved by an elevator-type mechanism which domain binds substrate and, through rigid body motions, transports it across membrane. To test this obtain more accurate descriptions alternate conformations proteins, we first performed collective variable-based steered molecular dynamics (CVSMD) simulations starting with crystal embedded model lipid bilayers, their toward own alternative conformation. Our show large rigid-body motions (55° rotation 8 A translation) lead access binding site side H-bonding interactions between are intact, although chains binding-site residues not restrained simulation. Pairs far apart structure become close each other simulated model. Some these pairs can cross-linked mercury ion when mutated cysteines, providing further support for CVSMD-generated In addition, maltose similar affinities before and after cross-linking, suggesting preserved after conformational change. combination, results EIIC.