Major intracellular localization of elongation factor-1

Polyclonal antibodies directed against the two components of EF-1, the G-protein EF-1 alpha and the guanine-nucleotide exchange complex EF-1 beta gamma delta, were used for the analysis of EF-1. We show that Xenopus oocytes as well as Xenopus A6 cultured cells contain comparable ratios around 2:1 of EF-1 alpha versus EF-1 beta gamma delta. Immunolocalization of EF-1 was analyzed in A6 cultured cells. Both components appeared to be mainly localized in the cytoplasmic compartment, as a granulous diffuse network forming a gradient from the nucleus to the periphery of the cells. The major fraction of EF-1 was correlated to endoplasmic reticulum localization and not to the microtubule network. Co-localization of EF-1 with the endoplasmic reticulum is consistent with the function of EF-1 in peptide chain elongation.