Int. J. Dev. Biol. 50: 341 - 358 (2006)

https://doi.org/10.1387/ijdb.052063jt

Vol 50, Issue 2-3

Special Issue: Developmental Morphodynamics

The evolution of the structure of tubulin and its potential consequences for the role and function of microtubules in cells and embryos

Open Access | Published: 15 February 2006

Jack A. Tuszynski^1,*, Eric J. Carpenter¹, J. Torin Huzil¹, Wojtek Malinski¹, Tyler Luchko¹ and Richard F. Luduena²

¹Department of Physics, University of Alberta, Edmonton, Alberta, Canada and ²Department of Biochemistry, MSC 7760, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA

Abstract

This paper discusses the results of homology modeling and resulting calculation of key structural and physical properties for close to 300 tubulin sequences, including alpha, beta, gamma, delta and epsilon -tubulins. The basis for our calculations was the structure of the tubulin dimer published several years ago by Nogales et al. (1998), later refined to 3.5 Å resolution by Löwe et al. (2001). While, it appears that the alpha, beta and gamma-tubulins segregate into distinct structural families, we have found several differences in the physical properties within each group. Each of the alpha, beta and gamma- tubulin groups exhibit major differences in their net electric charge, dipole moments and dipole vector orientations. These properties could influence functional characteristics such as microtubule stability and assembly kinetics, due to their effects on the strength of protein-protein interactions. In addition to the general structural trends between tubulin isoforms, we have observed that the carboxy-termini of alpha and beta-tubulin exists in at least two stable configurations, either projecting away from the tubulin (or microtubule) surface, or collapsed onto the surface. In the latter case, the carboxy-termini form a lattice distinctly different from that of the well-known A and B lattices formed by the tubulin subunits. However, this C-terminal lattice is indistinguishable from the lattice formed when the microtubule-associated protein tau binds to the microtubule surface. Finally, we have discussed how tubulin sequence diversity arose in evolution giving rise to its particular phylogeny and how it may be used in cell- and tissue-specific expression including embryonal development.

Keywords

tubulin, microtubule, isoform, homology model, dipole