The scientists identified the regulating element that is responsible for assembling a strong thread from the individual parts. It is the so-called C terminal domain of the silk protein. It prevents the formation of threads in the silk duct with its strong salt concentrations. In the spinning passage, however, where the salt concentration is low and sheer forces are abundant, this domain becomes instable and "sticky." This causes the chains to overlap and a strong spider silk thread is formed. The discovery of the significance of this relatively small C terminal domain, when compared to the overall length of the protein thread, was a sensation at the time and was published in the renowned scientific journal Nature.
Now the same group of researchers has put in place a further piece in the spider silk puzzle. They showed that the other end of the long thread, the so-called N terminal domain, plays an important role in the design of strong threads with great tensile strength. This time, the scientists investigated the head ends of the spider silk proteins of the "black widow" (Latrodectus hesperus). The result: The N terminal head ends exist in the silk duct as single strands (momomers). Only in the sinning passage are the head to tail pairs (dimers) formed.
The process of laying together is regulated via the change in pH values and salt concentrations between the silk duct and the spinning canal. In the silk duct, a neutral pH value of 7.2 and a high salt concentration prevent the N terminal head ends from combining. In the spinning passage, however, the environment becomes acidic (pH value around 6.2) the salt is removed. Now the ends can come together. In this process, the N terminal ends connect to the respective other ends a practically endless chain of linked up spider silk proteins is formed. "In our work we were able to show, in addition to our previous research, that bo
|Contact: Dr. Markus Bernards|
Technische Universitaet Muenchen