The Tubulin Tyrosination Cycle: A Palestinian Challenge

Microtubules are hollow rod-like polymers (figure 1). They fulfill a varied range of functions including maintenance of cell integrity, forming a spindle that facilitates chromosome separation and as a protein polymer ‘track’ for intracellular transport by molecular motors such as kinesin and dynein. Each microtubule is made of 13 protofilaments consisting of linearly arranged tubulin molecules. Each molecule is a dimer of two closely related monomers α and β tubulin, each having a molecular weight of 50 kDa. Tubulin dimers show micro-heterogeneity on Isoelectric focusing gels (figure 2) in part due to tubulin being encoded by a multi-gene family and in part due to an extensive range of posttranslational modifications. Tubulin’s posttranslational modifications are varied and include acetylation, glutamylation, glycation, phosphorylation and tyrosination. The atomic structure of the tubulin molecule was recently described (figure 3).