9hg8
BAM-SurA complex in the swing-out state with BamC resolved
Structural highlights
FunctionBAMA_ECOLI Part of the outer membrane protein assembly complex, which is involved in assembly and insertion of beta-barrel proteins into the outer membrane. Constitutes, with BamD, the core component of the assembly machinery.[1] [2] [3] [4] [5] Publication Abstract from PubMedThe proper folding of outer membrane proteins in Gram-negative bacteria relies on their delivery to the beta-barrel assembly machinery (BAM) complex. The mechanism by which survival protein A (SurA), the major periplasmic chaperone, facilitates this process is not well understood. We determine the structure of the holo insertase complex, where SurA binds BAM for substrate delivery. High-resolution cryo-electron microscopy structures of four different states and a three-dimensional variability analysis show that the holo insertase complex has a large motional spectrum. SurA bound to BAM can undergo a large swinging motion between two states. This motion is uncoupled from the conformational flexibility of the BamA barrel, which can open and close without affecting SurA binding. Notably, we observed conformational coupling of the SurA swing state and the carboxyl-terminal helix grip domain of BamC. Substrate delivery by SurA to BAM appears to follow a concerted motion that encodes a gated delivery pathway through the BAM accessory proteins to the membrane entry site. Architecture and conformational dynamics of the BAM-SurA holo insertase complex.,Lehner PA, Degen M, Jakob RP, Modaresi SM, Callon M, Burmann BM, Maier T, Hiller S Sci Adv. 2025 Apr 4;11(14):eads6094. doi: 10.1126/sciadv.ads6094. Epub 2025 Apr , 4. PMID:40184469[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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