Conformational dynamics of OMPs, periplasmic chaperones and BamA

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Outer membrane proteins maintain the viability of Gram-negative bacteria as receptors, transporters, ion channels, lipases, and porins. Folding and assembly of outer membrane proteins involves synchronized action of periplasmic chaperones and multi-protein machineries, which escort the highly hydrophobic polypeptides to their target outer membrane in a folding competent state. Over the past decades proteins and their biochemical function along the biogenesis pathway have been identified. Yet, the mechanisms of action and the intriguing ability of all these molecular machines to work without the typical cellular energy source of ATP, but solely based on thermodynamic principles are not well understood. In this application we aim to understand specific interactions of the periplasmic chaperones Skp and SurA with large outer membrane proteins, specific recognition sites and synergies of both chaperones. We will monitor these dynamics and structures using time-resolved single-molecule FRET, which allows us to reveal kinetics from the nanosecond to the minute timescale and spatial information from 2 to 8 nanometer. We further aim to reveal insights on the lateral gate dynamics of BamA and how those dynamics are influenced by the lipidic environment through reconstitution in artificial lipid bilayers and by preserving near native lipid compositions. We will further study how the lateral gate is influenced by other BAM proteins, by antibiotics and during insertion of OMP proteins. of the environment, direct interactions with other BAM proteins or antibiotics, and during insertion of OMP proteins.