Question

Which of the following ions are necessary for assembly of microtubules?

• A. Na${}^{+}$ and K${}^{+}$
• B. Ca${}^{++}$ and Cl${}^{-}$
• C. Ca${}^{++}$ and Mg${}^{++}$
• D. Na${}^{+}$ and Ca${}^{++}$

Answer 1

The correct option is C Ca${}^{++}$ and Mg${}^{++}$

Microtubules are unbranched hollow tubules of indefinite length about 25nm in thickness with 15nm core and boundary formed of 13 helically arranged protofilaments of globular molecules of $\alpha$ and $\beta$ tubulins. Lateral projections occur for establishing cross bridges. Tips of microtubules can grow and shorten quickly. GTP, calcium ions, magnesium ions and a calmodulin bound protein are required for their assembly.