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Identification of the Tubulin Gene Family and Sequence Determination of One β ‐Tubulin Gene in a Cold‐Poikilotherm Protozoan, the Antarctic Ciliate Euplotes focardii
Author(s) -
MICELI CRISTINA,
BALLARINI PATRIZIA,
GIUSEPPE GRAZIANO,
VALBONESI ALESSANDRO,
LUPORINI PIERANGELO
Publication year - 1994
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/j.1550-7408.1994.tb06100.x
Subject(s) - macronucleus , biology , tubulin , ciliate , gene , genetics , microtubule , tetrahymena , coding region , gene family , gene expression
. Four different tubulin genes were identified in the somatic nucleus (macronucleus) of Euplotes focardii , a strictly coldadapted, Antarctic ciliate: one of 1,800 bp for α‐tubulin and three of 2,150, 1,900, and 1,600 bp, respectively, for β ‐tubulin. Preliminarily analysed for restriction fragment length polymorphisms, these genes showed remarkable differences in organisation from tubulin genes of other ciliates which live in temperate areas and were analysed in parallel with E. focardii. The complete coding sequence of the 1,600 bp β ‐tubulin gene was then determined and shown to contain unique structural features of potential importance for E. focardii microtubule organization and activity. Of eight unique substitutions detected, seven were concentrated in the large amino terminal domain of the molecule that directly interacts with the carboxy terminal region of α‐tubulin for heterodimer formation. Sequence analysis of the cloned gene revealed, in addition, a potential new exception in the use of the genetic code by ciliates. A TAG codon was aligned in correspondence with Trp‐21 which is strictly conserved in every tubulin sequence so far determined.