2017/10/30 by Sami Chaaban, Gary J. Brouhard · 1 citation
Biochemistry, Genetics and Molecular Biology · Agricultural and Biological Sciences · #Microtubule and mitosis dynamics #Protist diversity and phylogeny #Chromosomal and Genetic Variations
paper · doi:10.1091/mbc.e16-05-0271
openalex publication_date 2017/10/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/16
Microtubules are long, slender polymers of αβ-tubulin found in all eukaryotic cells. Tubulins associate longitudinally to form protofilaments, and adjacent protofilaments associate laterally to form the microtubule. In the textbook view, microtubules are 1) composed of 13 protofilaments, 2) arranged in a radial array by the centrosome, and 3) built into the 9+2 axoneme. Although these canonical structures predominate in eukaryotes, microtubules with divergent protofilament numbers and higher-order microtubule assemblies have been discovered throughout the last century. Here we survey these noncanonical structures, from the 4-protofilament microtubules of Prosthecobacter to the 40-protofilament accessory microtubules of mantidfly sperm. We review the variety of protofilament numbers observed in different species, in different cells within the same species, and in different stages within the same cell. We describe the determinants of protofilament number, namely nucleation factors, tubulin isoforms, and posttranslational modifications. Finally, we speculate on the functional significance of these diverse polymers. Equipped with novel tubulin-purification tools, the field is now prepared to tackle the long-standing question of the evolutionary basis of microtubule structure.