Interaction of subunits of polypeptide chain elongation factor I from pig liver. Formation of EF-1alpha.EF-1betagamma and EF-1beta complexes.

In the preceding papers, we showed that one of the two complementar factors of polypeptide chain elongation factor 1 (EF-1) from pig liver, EF-1alpha, functionally corresponds to bacterial EF-Tu (Nagata, S., Iwasaki, K., and Kaziro, Y. (1976) Arch. Biochem. Biophys. 172, 168), while the other, EF-1betagamma, as well as one of its subunits, EF-1beta, corresponds to bacterial EF-Ts (Motoyoshi, K. and Iwasaki, K. (1977) J. Biochem. 82, 703). Therefore, the interaction between EF-1alpha and EF-1 betagamma or EF-1beta was was examined and the following results were obtained. i) EF-1betagamma catalytically promoted the exchange of [14C]GDP bound to EF-1alpha with exogenous [3H]GDP. ii). In the absence of the exogenous guanine nucleotide, EF-1betagamma as well as EF-1beta could displace GDP bound to EF-1alpha to form an EF-1alpha.EF-1betagamma as well as an EF-1alpha.EF-1beta complex. iii) The occurrence of EF-1alpha.EF-1betagamma and EF-1alpha.EF-1beta complexes was demonstrated by gel filtration on Sephadex G-150. These results strongly indicate that the mechanism of the action of EF-1betagamma or EF-1beta in converting EF-1alpha.GDP into EF-1alpha.GTP is analogous to bacterial EF-Ts, and the reaction is accomplished by the following reactions; EF-1alpha.GDP + EF-1betagamma (or EF-1beta) in equilibrium EF-1alpha.EF-1betagamma (or EF-1beta) + GDP; EF-1alpha.EF-1beta (or EF-1beta) + GTP IN EQUILIBRIUM EF-1alpha.GTP + EF-1betagamma (or EF-1beta).