STEROIDS, STEROID-BINDING PROTEINS AND HYDROPHOBIC BINDING SITES

摘要

Dorothy Crowfoot's first research assignment was to work on steroid structure, a controversial subject when she started her research. She completed this assignment in 1945 with the first three-dimensional structure of a steroid molecule, cholesteryl iodide. More recently, the structures of proteins which bind steroids have been determined. Some of them have a large closed cavity, big enough for the steroid nucleus, filled with up to 13 molecules of ordered water which must be displaced when a steroid is bound. Even more extensive arrays of ordered water molecules are observed in the binding cavity of some fatty acid-binding proteins. It is suggested that the function of these arrays of ordered water is to enhance the free energy released when a hydrophobic substrate is bound to them. This creates a favourable equilibrium which allows the enzymes to draw in these substrate molecules from their existing hydrophobic environment in micelles or membranes. [References: 35]