The mechanism for integration of α-helical membrane proteins into membranes has been well established. However, the mechanism for insertion of β-barrel membrane proteins, a unique type of membrane protein that can only be found in the outer membranes of Gram-negative bacteria, mitochondria, and chloroplasts, remains elusive. For Gram-negative bacteria, a five-component complex called the β-barrel assembly machinery (BAM) complex is required for membrane integration. To understand the mechanism of the BAM complex, we have determined crystal structures of BamA, a β-barrel membrane protein itself, in two different conformations representing open and closed states. The structure of BamA contains a C-terminal β-barrel domain consisting of 16-strands and a large periplasmic domain which sits in close proximity to the periplasmic face of the β-barrel domain in the closed state. Our studies suggest that BamA may function by priming the local membrane for insertion and may even undergo a lateral opening event during protein insertion. This work is supported by the Intramural Research Program of the NIH, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, 20892.
|Publication status||Published - 1 Apr 2013|