Translation elongation factor 1α (EF-1α) catalyzes the GTP-dependent binding of aminoacyl-tRNA to the ribosome. We previously reported that Tetrahymena EF-1α induced bundles of rabbit skeletal muscle F-actin as well as Tetrahymena F-actin (Kurasawa et al., (1996) Zool. Sci. 13: 371–375), and that Ca2 /calmodulin (CaM) regulated the F-actin-bundling activity of EF-1α without inhibition of the binding between EF-1α and F-actin (Kurasawa et al., (1996) J. Biochem. 119: 791–798). In this study, we investigated EF-1α-binding proteins in Tetrahymena using a Tetrahymena EF-1α affinity column. Tetrahymena EF-1α bound directly to 74 kDa, 77 kDa, and 78 kDa proteins, in addition to CaM. The bindings of 74 kDa, 77 kDa, and 78 kDa proteins to Tetrahymena EF-1α were Ca2 -independent and ATP-sensitive. The N-terminal amino acid sequence of the 74 kDa protein was similar to those of 70 kDa heat shock protein (hsp70) family.
