ABSTRACT
As discussed extensively in Chapter 12, the function of IDPs may occasionally stem directly from disorder. In these entropic chain functions, the lack of a stable structure of the polypeptide chain per se forms the basis of function, either due to the freedom in structural search it experiences or the force it can generate against effects that would reduce its conformational freedom. Here, we present a census of the four basic varieties of entropic chain functions. These are:
1. Linkers and spacers, which provide appropriate spatial separation and search of binding/catalytic domains or elements (e.g., linker region of cellulase E (von Ossowski et al. 2005))
2. Entropic bristles/brushes, which generate force against compression (e.g., microtubule-associated proteins (MAPs) (Mukhopadhyay and Hoh 2001))
3. Entropic springs, which generate force against physical extension (e.g., titin Pro, Glu, Val, Lys-rich (PEVK) domain (Trombitas et al. 1998))
4. Entropic clocks, which provide a timing function (voltage-sensitive K channel (Bentrop et al. 2001)).
