Divide and Conquer: A Tailored Solid-state NMR Approach to Study Large Membrane Protein Complexes

Membrane proteins are known to exert many essential biological functions by forming complexes in cell membranes. An example refers to the beta-barrel assembly machinery (BAM), a 200 kDa pentameric complex containing BAM proteins A-E that catalyzes the essential process of protein insertion into the outer membrane of gram-negative bacteria. While progress has been made in capturing three-dimensional structural snapshots of the BAM complex, the role of the lipoprotein BamC in the complex assembly in functional lipid bilayers has remained unclear. We have devised a component-selective preparation scheme to directly study BamC as part of the entire BAM complex in lipid bilayers. Combination with proton-detected solid-state NMR methods allowed us to probe the structure, dynamics, and supramolecular topology of full-length BamC embedded in the entire complex in lipid bilayers. Our approach may help decipher how individual proteins contribute to the dynamic formation and functioning of membrane protein complexes in membranes.

Automated summary

Membrane proteins play important biological roles by forming complexes in cell membranes. This study focuses on understanding the role of the lipoprotein BamC in the assembly of the beta-barrel assembly machinery (BAM) complex in lipid bilayers. By developing a selective preparation scheme and using proton-detected solid-state NMR methods, the researchers were able to investigate the structure and dynamics of BamC embedded in the entire BAM complex in lipid bilayers. This approach provides insights into the formation and functioning of membrane protein complexes.