Final answer:
The closure of the microtubule is accompanied by the hydrolysis of GTP bound to α/β-tubulin dimers, which is key for the dynamic instability that allows microtubules to assemble and disassemble as needed for cellular functions.
Step-by-step explanation:
The phenomenon that seems to accompany closure of the microtubule is hydrolysis of GTP bound to dimers. This process is crucial for the dynamic assembling and disassembling of microtubules. The GTP bound to the α/β-tubulin dimers provides the energy needed for their polymerization at the plus end of the microtubule. Upon incorporation into the microtubule, this GTP is hydrolyzed to GDP, which leads to a decrease in the stability of the microtubule structure, often triggering disassembly at the minus end.
During cellular activities such as cell division, microtubules undergo rapid phases of assembly and disassembly, which is essential for their function. The energy for these dynamic changes is derived from GTP hydrolysis, which is an exothermic reaction where GTP loses a phosphate group to become GDP. The release of energy during this reaction causes conformational changes in the tubulin dimers affecting the overall stability of the microtubule filament.