# User:Andy Maloney/Notebook/Lab Notebook of Andy Maloney/2009/05/08/Kinetic analysis of GTP hydrolysis associated with tubulin polymerization review

## Disclaimer

These are my thoughts on this paper. Read the paper before you read my comments please.

## Paper

Kinetic analysis of GTP hydrolysis associated with tubulin polymerization

## Review

So I started out with this question

- Question: How does tubulin polymerize into microtubules?

This paper gives me at least a reference for what is already known in the field and that is, tubulin carries GTP on both its [math]\displaystyle{ \alpha }[/math] and [math]\displaystyle{ \beta }[/math] subunits. When two tubulin heterodimers combine, the [math]\displaystyle{ \beta }[/math] site hydrolyzes GTP to form GDP. I think the GDP gets stuck but I'm not sure.

- They note that microtubules can be stabilized with nonhydrolyzable analogues of GTP such as GMPCPP.
- I got another reference where they actually show GTP hydrolysis occurs at the [math]\displaystyle{ \beta }[/math] subunit, Reference.
- They also state that free GTP in solution can be exchanged with bound GTP on tubulin that has been polymerized into microtubules.

**Take home**
This was a nice paper that answered the question for me of "where are the references that say GTP is needed". Of course, I still don't understand why polymerization needs magnesium ions.