Tubulin polymerization mixes containing Alexa 488-labeled tubulin (left), Alexa 594-labeled tubulin (center), and Cy5-labeled tubulin (right) at a 1:4 ratio with unlabeled tubulin.
GMPCPP is a slowly hydrolyzing analog of GTP and is therefore used to generate stable microtubules that resist depolymerization at room temperature. Short GMPCPP-stabilized microtubule “seeds” can serve as nucleation sites for microtubule elongation. By adding microtubule seeds to polymerization reactions, one can surpass the rate-limiting step of nucleation and specifically assess microtubule elongation. For more information on generating microtubule polymerization mixes visit the protocols Generating GMPCPP Stabilized Microtubules (for short, rigid microtubules) or Generating Taxol Stabilized Microtubules (for long, flexible microtubules).