Tubulin FAQs

Question 1:   What is the physiological form of tubulin?

Question 2:   What kits are available to study my protein of interest?

Question 3:  What assays are available to screen compounds for anti-microtubule activity?

Question 1: What is the physiological form of tubulin? 

Answer 1: The basic physiological unit of tubulin is the heterodimer, composed of 1 alpha and 1 beta subunit (aka alpha and beta tubulin).  A true monomer (either 1 alpha or 1 beta subunit) is unstable in vitro and is not known to exist under in vivo conditions. Molecular weight of the heterodimeric subunit is 110,000 daltons, whereas each monomer is 55,000 daltons.

Question 2: What kits are available to study my protein of interest?

Answer 2: Cytoskeleton, Inc. offers a variety of kits to study how a protein of interest interacts with and affects tubulin.  To examine if a protein is a microtubule binding protein (MAP), we offer the microtubule binding protein spin-down assay biochem kit (Cat. # BK029).  This kit provides clear instructions and all the reagents and controls necessary to determine the ability of a given protein to bind to tubulin monomers versus tubulin polymers (microtubules).  Tubulin binding can be measured by using a spin down assay where centrifugation is used to separate microtubules from tubulin monomers by differential sedimentation. 

We also offer absorbance and fluorescence-based tubulin polymerization assay Biochem Kits (Cat. # BK006P or BK011P, respectively) to follow polymerization kinetics.  There are many proteins and drugs that either enhance or inhibit polymerization.  These compounds can be characterized by their effect on one or more of the three stages of tubulin polymerization: nucleation, growth, and steady-state equilibrium.  A compound’s effects on depolymerization can also be evaluated.

We also offer kits that provide a convenient means of producing either fluorescently-labeled (Cat. # BK007R) or unlabeled (Cat. # BK015) microtubules for those researchers new to the tubulin field.  Additionally, the microtubule/tubulin in vivo assay kit (Cat. # BK038) offers a straightforward method for quantitating the in vivo ratio of tubulin polymers to monomers.  This kit allows the researcher to easily analyze changes in tubulin monomers and polymers induced by their protein of interest in cell or tissue samples.

To examine if your protein of interest affects how microtubules interact with kinesins, Cytoskeleton also offers ATPase assays that quantify the levels of inorganic phosphate production by microtubule-activated kinesin ATPase activity.  An end-point (Cat. # BK053) and kinetic (Cat. # BK060) kit is offered.

To examine site-specific competition for binding sites on tubulin, Cytoskeleton offers the tubulin ligand competition assay (Cat. # CDS15-P).  This kit allows for the screening and identification of new compounds that bind to known sites on the tubulin molecule. 

Question 3: What assays are available to screen compounds for anti-microtubule activity?

Answer 3: Cytoskeleton, Inc. supplies multiple kits that can be used to examine a compound’s anti-microtubule activity.  We offer absorbance and fluorescence-based tubulin polymerization assay Biochem Kits (Cat. # BK006P or BK011P, respectively) to follow polymerization kinetics.  The polymerization kits can be used to evaluate a compounds’s ability to induce microtubule depolymerization or impair polymerization.  We also offer kits that provide a convenient means of producing either fluorescently-labeled (Cat. # BK007R) or unlabeled (Cat. # BK015) microtubules.  These microtubules can then be incubated with compounds and changes in the length and number of microtubules can be quantified.  Additionally, the microtubule/tubulin in vivo assay kit (Cat. # BK038) offers a straightforward method for quantitating the in vivo ratio of tubulin polymers to monomers.  This kit allows the researcher to easily analyze changes in tubulin monomers and polymers induced by various treatment conditions in cell or tissue samples.