BamB

BamB (β‑barrel assembly machinery subunit B) is a peripheral lipoprotein that forms part of the BAM complex, an essential assembly system for outer‑membrane β‑barrel proteins in Gram‑negative bacteria. The bamB gene is typically located in an operon together with bamA, bamC and bamD, and the encoded protein is exported to the periplasm where it is lipid‑anchored to the inner leaflet of the outer membrane.

Functionally, BamB contributes to the stability and efficiency of the BAM complex, which catalyzes the insertion and folding of integral outer‑membrane proteins such as porins and transporters. Deletion of bamB in model organisms such as Escherichia coli results in reduced growth rates, heightened susceptibility to envelope stress, and defects in outer‑membrane protein assembly, although the complex remains partially functional, indicating that BamB is not absolutely essential but enhances overall efficiency.

Structurally, BamB consists of a series of tetratricopeptide‑like repeat domains that create a curved, solenoid architecture. Crystallographic studies reveal a largely β‑propeller fold with a central cavity that may accommodate nascent substrate proteins or interact with other BAM components. The lipidated N‑terminus anchors BamB to the membrane, positioning it adjacent to the core BamA protein, which contains the transmembrane β‑barrel and periplasmic POTRA domains.

BamB is conserved across many proteobacteria, with homologues identified in pathogens such as Salmonella, Pseudomonas and Neisseria species. Research suggests that BamB may influence bacterial virulence by modulating outer‑membrane composition and resistance to host defenses. Because of its role in outer‑membrane biogenesis, BamB is considered a potential target for novel antibacterial strategies aimed at compromising membrane integrity.