BamA

BamA, short for beta-barrel assembly machine A, is a central component of the β-barrel assembly machinery (BAM) in Gram-negative bacteria. It is an essential outer membrane protein responsible for the recognition, folding, and insertion of most newly synthesized outer membrane proteins (OMPs) into the outer membrane. BamA belongs to the Omp85 family of proteins and has homologs in mitochondria and chloroplasts (where they are known as Sam50 and related proteins).

Structurally, BamA comprises two main regions: an N-terminal periplasmic domain containing multiple POTRA (polypeptide-transport-associated) domains and a C-terminal integral β-barrel that resides in the outer membrane. In Escherichia coli, BamA contains five POTRA domains (POTRA1–POTRA5) preceding a 16-stranded β-barrel. The POTRA domains are thought to recruit substrate OMPs and interact with the other BAM components, while the β-barrel forms a lateral gate at the membrane interface to facilitate insertion of OMPs.

During biogenesis, BamA functions as the core of the BAM complex, coordinating with accessory lipoproteins BamB, BamC, BamD, and BamE to catalyze the folding and insertion of β-barrel OMPs. The complex is essential for outer membrane integrity and viability in most Gram-negative bacteria. Due to its central role and conservation, BamA is a frequent subject of antibiotic-target research aiming to disrupt outer membrane assembly.