Question

Explain how b-tubulin influences microtubule growth and shrinkage in the cell being sure to describe the change in state of GTP/GDP. Rubric (4): Nucleotide state of growing and shrinking microtubules is correctly described.

Answer 1

b-tubulin is actually made up of 13 protofilament. b-tubulin is the basic filament and make contact with lateral filaments. This filament has + and - end which is strictly participates in microtubules growth and shrinkage. In the stable state b-tubulin bound to GDP state but whether the growth or shrinkage occur is strictly depends on the GTP hydrolysis. Growth occurs at positive end of b-tubulin. When growth occurs GDP bound tubulin exchange with GTP and GTP hydrolysis helps to assemble the microtubule at + end.while GTP hydrolysis outpace the assembly and then GTP caped tubulin and high rate of GTP hydrolysis leads to shrinkage of microtubules.

As far as the nucleotide state concern growth of microtubule occurs when GTP bound tubulin state is doing and dessembly or shrinkage occur when GDP bound state is predominant.