The bacterial outer envelope is densely packed with proteins that form small pores and facilitate the passage of nutrients, toxins and signaling molecules. Professors Timm Maier and Sebastian Hiller from the Biozentrum of the University of Basel now demonstrate how these transporter proteins are integrated into the outer membrane. Using x-ray structural analysis they reveal the structure-function relationship of the protein TamA, which plays an important role in the assembly of transport proteins in the bacterial outer membrane. Their findings have been published recently in the renowned scientific journal Nature Structural and Molecular Biology.
Shuttling proteins from inside the cell to the outside environment is a complex task for Gram-negative bacteria, which are not only surrounded by an inner membrane, but also by an outer membrane barrier for protection against adverse environmental conditions. The bacteria however, can overcome this additional barrier by inserting special transport proteins into the protective outer membrane. In a joint project, Maier and Hiller, both Professors of Structural Biology at the Biozentrum of the University of Basel, provide mechanistic insights into this key process.
The structure of the assembly protein TamA explains its function
An important option for channeling protein domains across the outer membrane are so-called autotransporters. These membrane proteins form a barrel-like structure with a central pore, but they cannot autonomously transport their "passenger domain" across the outer membrane. Specific assembly proteins are required for the folding and integration of autotransporters into the outer membrane. Employing x-ray crystallography, the authors of the study decoded the atomic structure of the autotransporter assembly protein TamA of the intestinal bacterium Escherichia Coli.
"The protein TamA", explains Fabian Gruss, first author and recipient of a Werner-Siemen
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University of Basel