Building Blocks of the Outer Membrane: Calculating a General Elastic Energy Model for β‑Barrel Membrane Proteins

• Published in: Journal of chemical theory and computation Vol. 14; no. 8; pp. 4487 - 4497
• Main Authors: Lessen, Henry J., Fleming, Patrick J., Fleming, Karen G., Sodt, Alexander J.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.08.2018
• Subjects: Bacteria; Bacteria - chemistry; Bacterial Outer Membrane Proteins - chemistry; Barrels; Biomechanical Phenomena; Coding; Computation; Computer simulation; Elastic properties; Elasticity; Hydrogen Bonding; Hydrogen bonds; Lipids; Mechanical properties; Membranes; Molecular dynamics; Molecular Dynamics Simulation; Protein Structure, Secondary; Proteins; Stress, Mechanical
• ISSN: 1549-9618; 1549-9626
• DOI: 10.1021/acs.jctc.8b00377

The outer membranes of Gram negative bacteria are the first points of contact these organisms make with their environment. Understanding how composition determines the mechanical properties of this essential barrier is of paramount importance. Therefore, we developed a new computational method to measure the elasticity of transmembrane proteins found in the outer membrane. Using all-atom molecular dynamics simulations of these proteins, we apply a set of external forces to mechanically stress the transmembrane β-barrels. Our results from four representative β-barrels show that outer membrane proteins display elastic properties that are approximately 70 to 190 times stiffer than neat lipid membranes. These findings suggest that outer membrane β-barrels are a significant source of mechanical stability in bacteria. Our all-atom approach further reveals that resistance to radial stress is encoded by a general mechanism that includes stretching of backbone hydrogen bonds and tilting of β-strands with respect to the bilayer normal. This computational framework facilitates an increased theoretical understanding of how varying lipid and protein amounts affect the mechanical properties of the bacterial outer membrane.