Biochemical analysis of the interaction between elongation factor 1 alpha and alpha/beta-tubulins from a ciliate, Tetrahymena pyriformis

The interaction between elongation factor 1 alpha(EF-1 alpha) and alpha/bet a-tubulins has been analyzed in vivo and in vitro. An association of both a lpha- and beta-tubulins with EF-1 alpha in the lysate of Tetrahymena pyrifo rmis was detected by ca-immunoprecipitation analysis, In contrast, in vitro biomolecular interaction analysis with glutathione S-transferase (GST) fus ion proteins revealed that GST-beta-tubulin, but not GST-alpha-tubulin, can bind to GST-EF-1 alpha. Two beta-tubulin binding sites hale been identifie d to reside in the domains I and III of EF-1 alpha. In addition, beta-tubul in itself seems to have two distinct interaction sites for each of the doma ins. Since domain II of EF-1 alpha did not interact with beta-tubulin, we h ave re-evaluated the phylogenetic status of ciliates using EF-1 alpha seque nces devoid of domain II. The phylogenetic tree thus obtained was significa ntly different from that inferred from the whole sequence of EF-1 alpha, su ggesting the presence of functional constraints on the molecular evolution of EF-1 alpha. (C) 1999 Federation of European Biochemical Societies.