CHARACTERIZATION OF F-ACTIN BUNDLING ACTIVITY OF TETRAHYMENA ELONGATION-FACTOR 1-ALPHA INVESTIGATED WITH RABBIT SKELETAL-MUSCLE ACTIN

Elongation factor 1 alpha (EF-1 alpha) is an essential factor for prot ein synthesis in eukaryotes. Here, we demonstrated that Tetrahymena EF -1 alpha induced bundles of rabbit skeletal muscle F-actin as well as Tetrahymena F-actin in vitro, although Tetrahymena and skeletal muscle actins are different in some parts of their primary structures and in the binding abilities to some actin-binding proteins. Go-sedimentatio n experiments showed that the binding ratio of Tetrahymena EF-1 alpha to skeletal muscle F-actin in the bundles was 1 : 1. Electron microsco pic observation showed that alkaline pH or high ionic strength reduced the bundling activity of Tetrahymena EF-1 alpha to some extent, altho ugh the EF-1 alpha seemed to be able to induce bundling of the F-actin within the range of physiological condition.