FUNCTIONAL PROTEIN DOMAINS FROM THE THERMALLY DRIVEN MOTION OF POLYPEPTIDE-CHAINS - A PROPOSAL

It is proposed that the thermally driven motion of certain polypeptide chains, including those that are part of an otherwise stable folded p rotein, produces time-averaged three-dimensional domains that confer u nique functions to a protein. These domains may be controlled by colla psing the polypeptide into an enthalpically favored structure, or exte nding it into an entropically dominated form. In the extended form, th ese domains occupy a relatively large space, which may be used to regu late protein-protein interactions and confer mechanical properties to proteins. This ''entropic bristle'' model makes several predictions ab out the structure and properties of these domains, and the predictions are used to reevaluate a range of biophysical studies on proteins. Th e outcome of the analysis suggests that the entropic bristle can be us ed to explain a wide range of disparate and apparently unrelated exper imental observations. Proteins 32: 223-228, 1998, (C) 1998 Wiley-Liss, Inc.