Molecular snapshots reveal how bacteria assemble outer membrane proteins
Gram-negative bacteria are responsible for several infections that are hard to treat because of their high resistance to antibiotics. These bacteria possess an outermost layer called the outer membrane that acts as a protective barrier. Serving as the cell's interface with the outside world, the outer membrane contains specialized proteins that perform multiple functions, such as nutrient…
Gram-negative bacteria, notorious for their antibiotic resistance, possess an outer membrane serving as their protective barrier. This membrane houses specialized outer membrane proteins, which play crucial roles in nutrient transport and environmental sensing. The placement of these proteins is orchestrated by SurA, a chaperone, and the BAM complex. While SurA's role in delivering outer membrane proteins (OMPs) to BAM is understood, the precise mechanism of SurA's interaction with BAM has remained elusive.
A team of researchers led by Assistant Professor Ryoji Miyazaki from Nara Institute of Science and Technology (NAIST) aimed to elucidate this process. Their findings, published in Nature Communications, reveal that SurA adopts multiple conformations while interacting with BAM, pinpointing specific interactions that may facilitate OMP transfer.
The study, co-authored by researchers from NAIST, the University of Miyazaki, Indonesia, and the Japan Synchrotron Radiation Research Institute, used cryo-electron microscopy to capture four distinct structural snapshots of the SurA–BAM complex.
The structural analysis indicated that SurA undergoes large conformational changes to facilitate OMP delivery. The Core domain of SurA moves progressively closer to BAM, while its flexible P1 and P2 domains adopt different conformations. The P1 domain appears to regulate the Core domain's function, while the P2 domain interacts with BamE, a component of BAM, to position SurA near the assembly machinery. Disrupting the P2-BamE interaction diminished OMP assembly, underscoring its significance.
Given the outer membrane's critical role as a protective barrier in Gram-negative bacteria, understanding its assembly mechanism could potentially lead to novel strategies for weakening this barrier, thereby combating pathogenic or antibiotic-resistant bacteria. The research, conducted by an international team including scientists from Japan and Indonesia, opens new avenues for developing antibacterial agents targeting this essential cellular process.
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