Biochemical analysis of the interaction between elongation factor 1α and α/β‐tubulins from a ciliate, Tetrahymena pyriformis

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Abstract
The interaction between elongation factor 1α (EF‐1α) and α/β‐tubulins has been analyzed in vivo and in vitro. An association of both α‐ and β‐tubulins with EF‐1α in the lysate of Tetrahymena pyriformis was detected by co‐immunoprecipitation analysis. In contrast, in vitro biomolecular interaction analysis with glutathione S‐transferase (GST) fusion proteins revealed that GST‐β‐tubulin, but not GST‐α‐tubulin, can bind to GST‐EF‐1α. Two β‐tubulin binding sites have been identified to reside in the domains I and III of EF‐1α. In addition, β‐tubulin itself seems to have two distinct interaction sites for each of the domains. Since domain II of EF‐1α did not interact with β‐tubulin, we have re‐evaluated the phylogenetic status of ciliates using EF‐1α sequences devoid of domain II. The phylogenetic tree thus obtained was significantly different from that inferred from the whole sequence of EF‐1α, suggesting the presence of functional constraints on the molecular evolution of EF‐1α.