Some bacterial membrane transporters work almost like freight elevators to transport substances through the cell membrane into the interior of the cell. The transporter itself spans the bacterial membrane. Like a forklift, a soluble protein outside the bacterium transports the substance to the "elevator" and unloads its cargo there. The freight elevator transports it to the inside of the cell, in other words to another floor.

 

Researchers at the University Hospital Bonn (UKB) and the University of Bonn, in collaboration with a team from the University of York, have now studied the interaction between the transporter and its soluble substrate binding protein. Interestingly, they adapt precisely to each other during the transportation process. As this happens very quickly, the researchers virtually "blocked" the elevator by specifically inserting anchors, so-called disulphide bridges. This enabled them to prove that only the loaded "forklift" fits the "elevator" if it is on the right floor. This makes transportation really effective. Like all cells, bacteria are also surrounded by a cell membrane. This thin layer of lipids encloses nutrients, genetic material and proteins of the cell.

 

The TRAP transporter is supported by an additional substrate binding protein (SBP), which searches for sialic acid outside the bacterial membrane. Once this "forklift" has found a sugar molecule, the SBP changes its shape and binds the sialic acid tightly. It has long been suspected that the TRAP transporter recognizes the closed form of the substrate binding protein. The Bonn researchers therefore investigated whether the opening and closing of the SBP and the upward and downward movement of the TRAP transporter are actually coupled to each other. Because these movements are very fast, Hagelueken's team used what is known as disulphide engineering, a special biotechnological tool, to block the transporter. These new insights into the mechanism of the transporter may help in the future to develop antibiotics that ensure that the elevators of bacteria get stuck. This would put an end to the game of hide-and-seek and our immune system could destroy the bacteria more easily