b-Barrel proteins found in the outer membrane of Gram-negative bacteria serve a variety of cellular functions. Proper folding and assembly of these proteins are essential for the viability of bacteria and can also play an important role in virulence. The b-barrel assembly machinery (BAM) complex, which is responsible for the proper assembly of b-barrels into the outer membrane of Gram-negative bacteria, has been the focus of many recent studies. This review summarizes the significant progress that has been made toward understanding the structure and function of the bacterial BAM complex.
Background:The Escherichia coli -barrel assembly machinery complex (BamABCDE) facilitates outer membrane protein assembly.
Results:The unstructured N terminus of BamC binds and blocks the proposed substrate-binding pocket on BamD.
Conclusion:The unstructured N terminus of BamC is essential for BamCD interaction. Significance: The first Bam lipoprotein complex structure reveals how BamC and BamD interact.
In Gram‐negative bacteria, the BAM complex catalyzes the essential process of assembling outer membrane proteins. The BAM complex in Escherichia coli consists of five proteins: one β‐barrel membrane protein, BamA, and four lipoproteins, BamB, BamC, BamD and BamE. Here, the crystal structure of the C‐terminal domain of E. coli BamC (BamCC: Ala224–Ser343) refined to 1.5 Å resolution in space group H3 is reported. BamCC consists of a six‐stranded antiparallel β‐sheet, three α‐helices and one 310‐helix. Sequence and surface analysis reveals that most of the conserved residues within BamCC are localized to form a continuous negatively charged groove that is involved in a major crystalline lattice contact in which a helix from a neighbouring BamCC binds against this surface. This interaction is topologically and architecturally similar to those seen in the substrate‐binding grooves of other proteins with BamC‐like folds. Taken together, these results suggest that an identified surface on the C‐terminal domain of BamC may serve as an important protein‐binding surface for interaction with other BAM‐complex components or substrates.
BamB, BamC, BamD, and BamE are lipoproteins that, along with the integral membrane protein BamA, form the β-barrel assembly machinery (BAM) complex in the outer-membrane of Gram-negative bacteria. Elucidating the roles that these lipoproteins play in the β-barrel assembly process requires both structural and functional studies that rely on milligram quantities of pure protein. Here, we describe a simple protocol for expressing individual BamB-BamE proteins in Escherichia coli and purifying them by nickel affinity and size-exclusion chromatography. This protocol yields pure proteins in amounts that are sufficient for crystallization trials, in vitro protein-protein interaction studies, NMR, and other biochemical experiments.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.