Investigating the assembly and dynamics of the β-barrel assembly machinery in lipid environments with solid-state NMR

Abstract

The β-barrel assembly machinery (BAM) complex is an essential machinery in E. coli which is responsible for the correct folding and insertion of outer membrane β-barrel proteins into the outer membrane. Despite the wealth of information garnered from in vitro and in vivo experiments, debate still exists in regard to the mechanism employed by this machinery in an environment without external sources of energy. knowledge of the BAM complex is critical for understanding the mechanistic details of outer membrane protein biogenesis. Our goal was to study the BAM complex in an environment that mimics some of the characteristics of the outer membrane (lipid-to-protein ratio, lipid phase, hydrophobic thickness) whilst still allowing us to obtain such atomic level information. This information can then be transferred to studies of the BAM complex in its native environment. The studies described in this thesis relied on advancements in the field of solid-state NMR to be able to study such large membrane protein complexes, such as proton detection and dynamic nuclear polarization. The work described in this thesis is a significant advancement towards being able to study a large membrane protein complex in its native environment at the atomic level. Importantly, the approaches described are not restricted to the BAM but are generally applicable to large membrane protein complexes.