The structural biology of β-barrel membrane proteins: a summary of recent reports

The outer membranes of Gram-negative bacteria, mitochondria, and chloroplasts all contain transmembrane beta-barrel proteins. These beta-barrel proteins serve essential functions in cargo transport and signaling and are also vital for membrane biogenesis. They have also been adapted to perform a diverse set of important cellular functions including acting as porins, transporters, enzymes, virulence factors and receptors. Recent structures of transmembrane beta-barrels include that of a full length autotransporter (EstA), a bacterial heme transporter complex (HasR), a bacterial porin in complex with several ligands (PorB), and the mitochondrial voltage-dependent anion channel (VDAC) from both mouse and human. These represent only a few of the interesting structures of beta-barrel membrane proteins recently elucidated. However, they demonstrate many of the advancements made within the field of transmembrane protein structure in the past few years.