Membrane protein stability as the energy sink for sorting in the periplasm (224.3)

Abstract

We will present novel measurements of folding free energies for the transmembrane proteins PagP and OmpW from E. coli. Our data were collected in the same lipid bilayer and buffer system we previously employed to determine those parameters for E. coli OmpLA. From a biophysical perspective, our results suggest that the stabilities of these proteins may be strongly correlated to the water‐to‐bilayer transfer free energy of the lipid‐facing residues in their transmembrane regions. From a biological perspective, our findings suggest that the folding free energies for these membrane proteins may be the thermodynamic sink that establishes an energy gradient across the periplasm. This potential thus drives the sorting of outer membrane proteins by chaperones to the outer membranes in living bacteria. Binding free energies of these outer membrane proteins with periplasmic chaperones support this energy sink hypothesis.