Testis-specific ?2 tubulins are identical in Drosophila melanogaster and D. hydei but differ from the ubiquitous ?1 tubulin

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Abstract
In Drosophila as in many organisms β tubulins are encoded by a gene family. We have determined the complete nucleotide sequences coding for the β1 and β2 tubulins of Drosophila melanogaster and the β2 tubulin of D. hydei, and found these insect β tubulins to be highly conserved and like β tubulins of other organisms. This is discussed with reference to the possible functional domains of these proteins. — The β1 tubulin gene of Drosophila is constitutively expressed, whereas the β2 tubulin is expressed specifically in the testes. In D. melanogaster the amino acid sequences of these proteins are 95% homologous, differing at only 25 positions. In the testes the β2 tubulin participates in different microtubules as shown by genetic analysis (Kemphues et al. 1982). Interestingly, all of the amino acids characteristic of the testis-specific β2 tubulin are also present in the corresponding gene of D. hydei. Of special interest is the high degree of conservation of the carboxy-terminal domain in these functionally equivalent β tubulins.