Single alpha helical domains: designing artificial levers for biological molecules

点击翻译按钮获取中文摘要

DNA encodes the sequences of proteins, which consist of chains of amino acids that fold up into a precise 3 dimensional structure. Proteins are essential for life, and the structures of different proteins specify how they work in cells, for example as an enzyme or as a structural protein. Discovering the principles that govern how proteins fold up into their three dimensional structure, is therefore key to understanding life, in understanding what goes wrong in disease, and in designing new proteins with useful properties that would, for instance, enable us to target man-made drugs to disease targets such as cancerous cells. Folded proteins contain a series of well-defined structural building blocks. One of these is the alpha helix, which looks a little like a coiled spring. To understand how proteins fold up into their three dimensional structure, the properties of alpha-helices have been intensively studied. In most cases, alpha-helices are not very stable by themselves in water: they collapse into a randomly folded chain. However, we have recently found that there is one type of naturally occurring alpha helix that is remarkably stable all on its own in water. This stable alpha helix is found in a wide variety of proteins from bacteria to humans, including in proteins important for cell movement and cell division. At the moment, we know very little about what makes it so stable, or what its function in protein is. It is usually found sandwiched between two regions of the protein in such a way that we think they might act as stiff linkers (or struts) between the two parts of the protein, and transmit information about changes in structure in one part of the protein to the other part. We want find out what makes these alpha helices so stable, and to test our ideas about what they do, by determining the mechanical properties of artificial and naturally occurring alpha-helices that we think form stable alpha helices in water. To learn as much as possible in a short time, we want to have two researchers with different skills working together to study these helices one molecule at a time. One of them will engineer a series of proteins containing these alpha helices and determine how their function depends on the sequence of the amino acids. The other researcher will find out the mechanical properties of each of these engineered proteins using a new apparatus that lets us study how a single molecule unfolds when it is stretched and refolds when it is released, and will also create models in the computer to explain the results and predict new properties. They will also send these proteins to our collaborators in the USA who can discover additional properties of them using their own specialized methods. By using as wide a range of techniques as possible, to study this stable alpha helix, we think we will determine why it is so stable, and what proteins need it for.