Biochemistry 4th Edition by Christopher Mathews,Kensal van Holde, Dean Appling, Spencer Anthony Cahill

Exercise 4

Tubulin binds GTP, and the polymerization of a microtubule is greatly stimulated when a tubulin molecule at the growing end carries GTP. Tubulin also has a GTPase activity, with a low-turnover number. Microtubules carrying GDP at their ends are more likely to lose tubulin monomers. Show how these facts can explain the remarkable observation that at certain GTP levels some microtubules in a mixture will grow while others simultaneously shrink.