The microtubule lattice: a brief historical perspective.

At first glance, the structure of a microtubule is simple. Globular α- and β-tubulin subunits form constitutive heterodimers that align head-to-tail in protofilaments. In the most common configuration, 13 protofilaments associate laterally with a slight longitudinal stagger that results in a left-handed 3-start helix featuring lateral associations between tubulin subunits. This seemingly straightforward description is actually based on almost half a century of research aimed at understanding how tubulin dimers interact within the microtubule lattice. But while we start to have a good overview of their architecture in vitro, our knowledge of microtubule-lattice organization in vivo is nowhere near to being complete.