Perspectives on tubulin isotype function and evolution based on the observation that Tetrahymena thermophila microtubules contain a single alpha- and beta-tubulin

Cell Motil Cytoskeleton. 1993;25(3):243-53. doi: 10.1002/cm.970250305.


We have cloned and sequenced the two beta-tubulin genes of the ciliated protozoan Tetrahymena thermophila. The two genes encode identical 443 amino acid peptides which are 99.7% identical to the beta-tubulin proteins of T. pyriformis and 95% identical to human beta 1 tubulin. T. thermophila contains only one alpha-tubulin gene (Callahan et al., 1984: Cell 36:441-445). Thus, all of the extremely diverse microtubule structures in this unicellular organism can be formed from a single alpha- and a single beta-tubulin peptide. We have also carried out a phylogenetic analysis of 84 complete beta-tubulin peptide sequences. This analysis supports two hypotheses regarding beta-tubulin evolution and function: 1) Multifunctional beta-tubulins are under greater evolutionary constraint than beta-tubulins present in specialized cells or in cells with very few microtubule related functions, which can evolve rapidly; and 2) Cells which form axonemes maintain a homogeneous population of tubulins.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • DNA / genetics
  • Microtubules / chemistry*
  • Microtubules / physiology*
  • Molecular Sequence Data
  • Phylogeny
  • Tetrahymena pyriformis
  • Tetrahymena thermophila / genetics
  • Tetrahymena thermophila / physiology*
  • Transcription, Genetic
  • Tubulin / analysis*
  • Tubulin / genetics
  • Tubulin / physiology*


  • Tubulin
  • DNA

Associated data

  • GENBANK/L01415
  • GENBANK/L01416
  • GENBANK/Z25423
  • GENBANK/Z25424
  • GENBANK/Z25425
  • GENBANK/Z25426
  • GENBANK/Z25427
  • GENBANK/Z25428
  • GENBANK/Z25429
  • GENBANK/Z25430