Similar to expansin

Once the work had been accomplished the protein was the object of different studies at the CIP. In this way another researcher, a bacteriologist at the CIP, showed in particular that EXLX1 indeed effectively plays a role in the maintenance of the protective net that envelops the bacteria. The protein in fact accelerates the decomposition of this protective wall. And when EXLX1 is not there the bacteria dies less quickly. But it was via an email from the United States that research on this protein took an unexpected turn. ‘The structure of our protein was published in a database used by specialists the world over: www.pdb.org,’ explains Frédéric Kerff. ‘And an American researcher noticed that it possessed a structure very similar to the plant proteins he was studying, expansins. It was the first time that this type of protein had been brought to light in an organism other than a plant. This bacterial curiosity sparked his interest and we began a collaboration.’

Expansin is a very important protein in the plant world. It allows a plant to become longer and to grow without becoming weakened. A relatively straightforward experiment demonstrates this. The first step: cut a shoot from no matter what plant. Second step: destroy everything which is living inside the shoot in such a way that only the shoot’s envelope survives. Third step: apply mechanical pressure on both sides of the stem. And the final step: add to the plant tissue a good dose of expansin. It’s done! Even though it has been emptied of all its internal resources, the shoot grows longer, and without breaking. Expansins allow cellulose fibres to stretch when they are put under strain but the mechanics of how they act are still poorly understood. They play an important role during phases of cellular expansion as well as in other phenomena involving a modification of the cell well: cell separation, leaf formation, ripening of fruit...