The subunit structure of elongation factor 1 from Artemia. Why two alpha-chains in this complex?

Elongation factor 1 (EF-1) regulates the specific interaction of aminoacyl-tRNA with the ribosome during the elongation phase of protein biosynthesis. Although individual functions of its separate chains have been well defined, to date there is hardly information about the structure and function of the whole complex. We describe here the complete subunit structure of elongation factor 1, and discuss its change during development of Artemia. Elongation factor 1 consists of a pentameric complex, composed of four different subunits alpha, beta, gamma, and delta in a molar ratio of 2:1:1:1. Although one molecule of EF-1 alpha dissociates easily from the complex EF-1 alpha 2 beta gamma delta under the influence of aminoacyl-tRNA and GTP, the second molecule of EF-1 alpha was found to remain firmly attached. Thus, in eukaryotic protein synthesis, movement of transfer RNAs to the ribosome seems under the influence of two distinct molecules of EF-1 alpha, a result possibly related to the presumed consumption of two molecules of GTP by EF-Tu during the elongation step of prokaryotic protein synthesis.