Elongation factor 1β is an actin-binding protein

A 17 kDa polypeptide found in association with actin in cellular extracts of Dietyostelium discoideum was identified as a proteolytic fragment of eEF1 beta. Antibody elicited against the 17 kDa protein reacted with a single 29 kDa polypeptide in Dictyostelium, indicating that the 17 kDa peptide arises from degradation of a larger precursor. The cDNA isolated from a Dictyostelium library using this antibody as a probe encodes Dictyostelium elongation factor lp. Amino acid degradation of the 17 kDa protein fragment confirmed the identity of the protein as eEF1 beta. Direct interaction of cEF1 beta with actin in vitro was further demonstrated in mixtures of actin with the 17 kDa protein fragment of Dietyostelium eEF1 beta, recombinant preparations of Dietyostelium eEF1 beta expressed in Escherichia coli, and the intact eEF1 beta gamma complex purified from wheat germ. Localization of cEF1 beta in Dictyostelium by immunofluorescence microscopy reveals both diffuse cytoplasmic staining, and some concentration in the cortical and hyaline cytoplasm. The results support the existence of physical and functional interactions of the translation apparatus with the cytoskeleton, and suggest that eEF1 beta may function in a dual role both to promote the elongation phase of protein synthesis, and to interact with cytoplasmic actin. (C) 2001 Elsevier Science B.V. All rights reserved.