title: Perspectives on tubulin isotype function and evolution based on the observation that Tetrahymena thermophila microtubules contain a single alpha- and beta-tubulin.
abstract: 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.
authors.affiliation: Department of Biology, University of Rochester, NY 14627.
authors.forename: J
authors.initials: J
authors.lastname: Gaertig
authors.forename: T H
authors.initials: TH
authors.lastname: Thatcher
authors.forename: K E
authors.initials: KE
authors.lastname: McGrath
authors.forename: R C
authors.initials: RC
authors.lastname: Callahan
authors.forename: M A
authors.initials: MA
authors.lastname: Gorovsky
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D008870:Microtubules / Q000737:chemistry* / Q000502:physiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D013769:Tetrahymena pyriformis; D016808:Tetrahymena thermophila / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D014404:Tubulin / Q000032:analysis* / Q000235:genetics / Q000502:physiology*
chemical_list: D014404:Tubulin; D004247:DNA