Evolution of protein intrinsic disorder

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***(This is a summary written simply, for the public to read, as per the NSERC instructions:-)****** Proteins are long molecules made of strings of small building blocks, called 'amino acids'. These amino acids have many different characters. Proteins do many different jobs in living organisms. They harvest energy, they transport and change chemicals, and form scaffolds for cells and tissues. Most proteins have a fixed shape or set of shapes that are designed for whatever job(s) they do. Some protein or protein parts, however, do not have a fixed shape, but instead they have a constantly changing shape, jiggling around like a string that never stays in one arrangement. These are called 'intrinsically disordered'. They use very different combinations of amino-acid building blocks to those that have a 'fixed shape'. *** As organisms evolve across many millions of years, the proteins in their cells and tissues also evolve and mutate, and take on new roles or modified old roles. By studying how this happens, we can figure out which parts of proteins are important for their jobs, and which are not. Also, examining how proteins evolve helps us to figure out whether the proteins are related to each other, or can do similar jobs. *** This process of studying the evolution of proteins is well understood for 'fixed-shape' proteins or protein parts. However, it is not well understood for the 'intrinsically disordered'. In this work, we are aiming to discover more about how intrinsically disordered proteins and protein parts evolve. *** In the right environments or contexts, some intrinsically disordered proteins can occasionally take on a fixed shape, that can be passed on to other copies of the same proteins. The proteins then all bundle together in protein assemblies called 'prions', that keep replicating the fixed shapes by passing them onto more and more of the intrinsically disordered proteins. The shapes of these prions are called 'amyloids'. These amyloids are long, twisted fibres that are also linked to a lot of human diseases of the brain and nervous system. We also study the evolution of these 'prion-forming' proteins and proteins that look like them. *** This work will advance our general knowledge of how proteins evolve, and how general mutation trends (that arise across all proteins in an organism) occur and affect individual protein evolution. This work will also help us to find and understand the important intrinsically disordered parts of proteins that are functional, and that are thus useful for biotechnology and, where they are linked to disease mechanisms, are potential targets for drug design. By understanding what parts of prion and prion-like proteins are functionally important and by analyzing how different parts of prion sequences evolve, we will be able to gain insights into the origins of similar proteins that are linked to human diseases. These advances will useful for humans in Canada and around the world. **