Proteins play a vital role in the structure and functioning of all forms of life. They catalyse the reactions within living systems and are responsible for signalling and communication within cells.
Each protein is a long-chain molecule that contains between 50 and 1000 smaller molecular units known as amino acids. These basic building blocks come in 20 naturally occurring varieties and are mostly made up of carbon, hydrogen, oxygen and nitrogen.
However, a long, 1-D chain of amino acids does not immediately function as a protein just by having the various building blocks in the correct order. The way that the 1-D chain molecule "folds up" to form a 3-D structure is crucial. It is only when the protein has folded into an organized 3-D structure that it can perform its biological function.
The final shape of the protein determines its biological function - only some molecules will fit into the folds, loops and spirals in the folded 3-D structure. For example, digestive enzymes trap food molecules into their folds, placing them precisely near those molecular groups that can specifically break them down. So how does the sequence of amino acids "tell" the protein molecule to organize itself into a specific conformation that is capable of functioning? And how does the molecule fold so quickly into its final shape? These questions raise important new issues for physical scientists.
In the September issue of Physics World magazine, Peter Wolynesfrom the University of Illinois, Urbana, USA and William Eaton from the National Institutes of Health, Bethesda, also in the USA, explain the latest research into protein folding.