The lateral gate of BamA is associated with the POTRA domains and accessory proteins

Outer membrane proteins (OMPs) in Gram-negative bacteria are transmembrane β-barrel proteins that are involved in many processes. The complex for insertion and assembly of OMPs is the β-barrel assembly machinery (BAM). There are two leading models for this insertion process based on features proximal to the seam between the N-terminal (β1) and C-terminal (β16) strands of the BamA β-barrel: the assisted model and the budding model. While both models are backed by experimental evidence, no conclusive study yet exists. Molecular dynamics is performed to identify key interactions for the insertion process. Using the previously identified crystal structures, we carried out microsecond-long equilibrium simulations of BAM complex systems with an open or a closed lateral gate and with or without the lipoprotein BamB. We discovered that the laterally open structure is unstable in the absence of accessory proteins and the rotational movement of the accessory proteins drives lateral gate dynamics